part iv: texas instruments ti-89 graphing calculator iv.1 getting started … · 2008-06-27 ·...

Part IV: Texas Instruments TI-89 Graphing Calculator

IV.1 Getting started with the TI-89

IV.1.1 Basics: Press the ON key to begin using your TI-89. If you need to adjust the display contrast, firstpress and hold , then press (the minus key) to lighten or + (the plus key) to darken. When you havefinished with the calculator, turn it off to conserve battery power by pressing 2nd and then OFF.

Check our TI-89’s settings by pressing MODE. If necessary, use the arrow keys to move the blinking cursorto a setting you want to change. You can also use F1 to go to page 1, F2 to go to page 2, and F3 to go topage 3 of the MODE menu. To change a setting, use to get to the setting that you want to change, thenpress to see the options available. Use or to highlight the setting you want and press ENTER toselect the setting. To start with, select the options shown in Figures IV.1, IV.2, and IV.3: function graphs,main folder, floating decimals with 10 digits displayed, radian measure, normal exponential format, realnumbers, rectangular vectors, pretty print, full screen display, home screen showing, approximatecalculation mode, decimal base, international system of units (metric measurement), and English. Note thatsome of the lines on page 2 and page 3 of the MODE menu are not readable. These lines pertain to optionsthat are not set as above. Details on alternative options will be given later in this guide. For now, leave theMODE menu by pressing HOME or 2nd QUIT. Some of the current settings are shown on the status lineof the home screen.

Figure IV.1: MODE menu, page 1 Figure IV.2: MODE menu, page 2

Figure IV.3: MODE menu, page 3

�

Graphing Technology Guide Copyright © by Houghton Mifflin Harcourt Publishing Company. IV-1All rights reserved.

In this guide, the key with the green diamond symbol inside a green border will be indicated by , thekey with the white arrow pointing up inside a white border (the shift key) will be indicated by , andthe key with the white arrow (the backspace key) pointing to the left will be indicated by .

There are 5 blue keys below the calculator screen labeled F1 through F5. These function keys havedifferent effects depending on the screen that is currently showing. The effect or menu of the functionkeys corresponding to a screen are shown across the top of the display.

IV.1.2: Editing: One advantage of the TI-89 is that you can use the arrow keys to scroll in order to see along calculation. For example, type this sum (Figure IV.4):

Then press ENTER to see the answer. The sum is too long for both the entry line and the history area. Thedirection(s) in which the line extends off the screen is indicated by an ellipsis at the end of the entry line andarrows or in the history area. You can scroll through the entire calculation by using or to put

the cursor on the appropriate line and then using or to move the cursor to the part of the calculation thatyou wish to see.

Figure IV.4: Home screen

Often we do not notice a mistake until we see how unreasonable an answer is. The TI-89 permits you toredisplay an entire calculation, edit it easily, then execute the corrected calculation.

Suppose you had typed as in Figure IV.5 but had not yet pressed ENTER, when you realizethat 34 should have been 74. Simply press as many times as necessary to move the blinking cursor lineuntil it is to the immediate right of the 3, press to delete the 3, and then type 7. On the other hand if 34should have been 384, move the cursor until it is between the 3 and the 4 and then type 8. If the 34 shouldhave been 3 only, move the cursor to the right of the 4, and press to delete the 4.

Figure IV.5: Editing a calculation

Technology Tip: The TI-89 has two different inputting modes: insert and overtype. The default mode isinsert mode, in which the cursor is a blinking vertical line and new text will be inserted at the cursor’sposition and other characters are pushed to the right. In the overtype mode, the cursor is a blinking squareand the characters that you type replace the existing characters. To change from one mode to another, press2nd INS. The TI-89 remains in whatever the last input mode was, even after being turned off.

12 � 34 � 56

��

1 � 2 � 3 � 4 � 5 � 6 � 7 � 8 � 9 � 10 � 11 � 12 � 13 � 14 � 15 � 16 � 17 � 18 � 19 � 20

IV-2 Copyright © by Houghton Mifflin Harcourt Publishing Company. TI-89 Graphing CalculatorAll rights reserved.

Even if you had pressed ENTER, you may still edit the previous expression. Immediately after you pressENTER your entry remains on the entry line. Pressing moves the cursor to the beginning of the line, while

pressing puts the cursor at the end of the line. Now the expression can be edited as above. To edit aprevious expression that is no longer on the entry line, press 2nd and then ENTRY to recall the priorexpression. Now you can change it. In fact, the TI-89 retains as many entries as the current history area holdsin a “last entry” storage area, including entries that have scrolled off the screen. Press 2nd ENTRYrepeatedly until the previous line you want is on the entry line. (The number of entries that the history areacan hold may be changed, see your user’s manual for more information.)

To clear the entry line, press CLEAR while the cursor is on that line. To clear previous entry/answer pairsfrom the history area, use or to move the cursor to either the entry or the answer and press CLEAR(both the entry and the answer will be deleted from the display). To clear the entire history area, press F1[Tools] 8 [Clear Home], although this will not clear the entry line.

Technology Tip: When you need to evaluate a formula for different values of a variable, use the editingfeature to simplify the process. For example, suppose you want to find the balance in an investment accountif there is now $5000 in the account and interest is compounded annually at the rate of 8.5%. The formula

for the balance is where principal, rate of interest (expressed as a decimal),

number of times interest is compounded each year, and number of years. In our example, thisbecomes Here are the keystrokes for finding the balance after 3, 5, and 10 years(results are shown in Figure IV.6).

Years Keystrokes Balance

3 5000 (1 + .085) ^ 3 ENTER $6386.45

5 5 ENTER $7518.28

10 10 ENTER $11,304.92

Figure IV.6: Editing expressions

Then to find the balance from the same initial investment but after 5 years when the annual interest rate is 7.5%, press the following keys to change the last calculation above: 5 7 ENTER.You could also use the CLEAR key to erase everything to the right of the current location of the cursor. Then,changing the calculation from 10 years at the annual interest rate of 8.5% to 5 years at the annual interestrate of 7.5% is then done by pressing CLEAR 5 7 ENTER.

IV.1.3 Key Functions: Most keys on the TI-89 offer access to more than one function, just as the keys on acomputer keyboard can produce more than one letter (“g” and “G”) or even quite different characters (“5”and “%”). The primary function of a key is indicated on the key itself, and you access that function by asimple press on the key.

To access the second function indicated in yellow or to the left above a key, first press 2nd (“2nd” appearson the status line) and then press the key. For example, to calculate press 2nd 25 ) ENTER.� �25

t �5000�1 � .085�t.t �n �

r �P �P � �1 �r

n�nt

,


Technology Tip: The TI-89 automatically places a left parenthesis, (, after many functions and operators(including 2nd LN, , 2nd SIN, 2nd COS, 2nd TAN, and 2nd ). If a right parenthesis is notentered, the TI-89 will respond with an error message indicating that the right parenthesis is missing.

When you want to use a function printed in green or to the right above a key, first press (“◆” appears onthe status line) and then press the key. For example, if you are in exact calculation mode and want to find theapproximate value of press 2nd 45 ) .

The TI-89 can produce both upper and lower case letters. When you want to use a lower case letter printedin purple or to the right above a key, first press alpha (a lower case “a” appears on the status line) and pressthe key. For example, to use the letter k in a formula, press alpha K. If you need several letters in a row,press 2nd a-lock, and then press all the letters you want. Remember to press alpha when you are finishedand want to restore the keys to their primary functions. To type upper case letters, press and then pressthe letter. To lock in upper case letters, press alpha (an upper case “A” appears on the status line). To restore the keys to their primary functions, press alpha.

Technology Tip: There are separate keys for the commonly used letters X, Y, Z, and T. A simple press of thekey will produce a lower case letter while pressing and then the key will produce an upper case letter.

IV.1.4 Order of Operations: The TI-89 performs calculations according to the standard algebraic rules.Working outwards from inner parentheses, calculations are performed from left to right. Powers and rootsare evaluated first, followed by multiplications and divisions, and then additions and subtractions.

Note that the TI-89 distinguishes between subtraction and the negative sign. If you wish to enter a negativenumber, it is necessary to use the (-) key. For example, you would calculate by pressing(-) 5 (4 (-) 3) ENTER to get 7.

Enter these expressions to practice using your TI-89.

Expression Keystrokes Display

7 5 3 ENTER -8

(7 5) 3 ENTER 6

120 10 ^ 2 ENTER 20

(120 10) ^ 2 ENTER 12100

24 ÷ 2 ^ 3 ENTER 3

(24 ÷ 2) ^ 3 ENTER 1728

(7 (-) 5) (-) 3 ENTER -36

IV.1.5 Algebraic Expressions and Memory: Your calculator can evaluate expressions such as

after you have entered a value for Suppose you want Press 200 STO alpha N ENTER tostore the value 200 in memory location Whenever you use in an expression, the calculator willsubstitute the value 200 until you make a change by storing another number in Next, enter the expression

by typing alpha N (alpha N + 1) ÷ 2 ENTER. For you find that

Note that there is no distinction made between upper and lower case letters in this case.

The contents of any memory location may be revealed by typing just its letter name and then ENTER. Andthe TI-89 retains memorized values even when it is turned off, so long as its batteries are good.

N�N � 1�2

� 20,100.

N � 200,�N�N � 1�

2

N.NN.

�N � 200.N.

N�N � 1�2

��7 � �5� � �3

�242 �

3

2423

�120 � 10�2�

120 � 102�

�7 � 5� � 3��

7 � 5 � 3��

��5 � ��4 � �3�

�� 45

� ex


IV.1.6 Repeated Operations with ANS: As many entry/answer pairs as the history area shows are stored inmemory. The last result displayed can be entered on the entry line by pressing 2nd ANS, while the last entrycomputed is entered on the entry line by pressing 2nd ENTRY. This makes it easy to use the answer fromone computation in another computation. For example, press 30 + 15 ENTER so that 45 is the last resultdisplayed. Then press 2nd ANS ÷ 9 ENTER and get 5 because

The answer locations are indexed by ans(#), where # indicates the number of the answer. The pairs arenumbered with the most recent computation as 1. So, the number of a pair changes with each successivecomputation that is entered. The number of an entry or answer can be found by using to scroll up tothe entry or answer. The number, which is the same for both the entry and the answer, is shown on thestatus line.

To use an earlier answer or entry in a computation, to calculate, say 15 times answer 3 plus 75, press 15 2nd a-lock A N S alpha ( 3 ) + 75 ENTER.

With a function like division, you press after you enter an argument. For such functions, whenever youwould start a new calculation with the previous answer followed by pressing the function key, you may pressjust the function key. So instead of 2nd ANS ÷ 9 in the previous example, you could have pressed simply9 to achieve the same result. This technique also works for these functions: + – ^.

Here is a situation where this is especially useful. Suppose a person makes $5.85 per hour and you are askedto calculate earnings for a day, a week, and a year. Execute the given keystrokes to find the person’s incomesduring these periods (results are shown in Figure IV.7).

Pay Period Keystrokes Earnings

8-hour day 5.85 8 ENTER $46.80

5-day week 5 ENTER $234

52-week year 52 ENTER $12,168

Figure IV.7: ANS variable

IV.1.7 The MATH Menu: Operators and functions associated with a scientific calculator are available eitherimmediately from the keys of the TI-89 or by the 2nd keys. You have direct access to common arithmeticoperations (2nd , ^), trigonometric functions (2nd SIN, 2nd COS, 2nd TAN), and their inverses ( , , ), exponential and logarithmic functions (2nd , 2nd LN), and afamous constant (2nd ).

A significant difference between the TI-89 graphing calculators and most scientific calculators is that TI-89requires the argument of a function after the function, as you would see in a formula written in yourtextbook. For example, on the TI-89 you calculate by pressing the keys 2nd 16) in that order.� �16

�exTAN-1COS-1SIN-1

�

�

�

�

�

�

�

�

45 � 9 � 5.


Here are keystrokes for basic mathematical operations. Try them for practice on your TI-89.


2nd 3 ^ 2 + 4 ^ 2 ) ENTER 5

2 + 3 ^ (-) 1 ENTER 2.333333333

ln 200 2nd LN 200 ) ENTER 5.298317367

2.34 10 ^ 5 ENTER 234000

Technology Tip: Note that if you had set the calculation mode to either AUTO or EXACT (page 2 of theMODE menu), the TI-89 would display for and ln 200 for ln 200. So, you can use either fractions andexact numbers or decimal approximations. The AUTO mode will give exact rational results whenever all ofthe numbers entered are rational, and decimal approximations for other results.

Additional mathematical operations and functions are available from the MATH menu. Press 2nd MATH tosee the various sub-menus (Figure IV.8). Press 1 [Number] or just ENTER to see the options available underthe Number sub-menu (Figure IV.9). You will learn in your mathematics textbook how to apply many ofthem. As an example, calculate the remainder of 437 when divided by 49 by pressing 2nd MATH 1[Number] then either alpha A [remain( ] or ENTER; finally press 437 , 49) ENTER to see 45. To leave the MATH menu (or any other menu) and take no other action, press 2nd QUIT or just ESC.

Note that you can select a function or a sub-menu from the current menu by pressing either until thedesired item is highlighted and then ENTER, or by pressing the number or letter corresponding to thefunction or sub-menu. It is easier to press alpha A than to press nine times to get the remain( function.

Figure IV.8: MATH menu Figure IV.9: Number sub-menu

The factorial of a nonnegative integer is the product of all the integers from 1 up to the given integer. Thesymbol for factorial is the exclamation point. So 4! (pronounced four factorial ) is Youwill learn more about applications of factorials in your textbook, but for now use the TI-89 to calculate 4!.The factorial command is located in the MATH menu’s Probability sub-menu. To compute 4!, press thesekeystrokes: 4 2nd MATH 7 [Probability] 1 [ ! ] ENTER.

On the TI-89 it is possible to do calculations with complex numbers. To enter the imaginary number i, press2nd i. For example, to divide by press (2 + 3 2nd i ) ÷ (4 2 2nd i ) ENTER. The resultis (Figure IV.10).

To find the complex conjugate of press 2nd MATH 5 [Complex] 1 [conj( ] 4 + 5 2nd i ) ENTER(Figure IV.10).

4 � 5i

0.1 � 0.8i�4 � 2i,2 � 3i

1 � 2 � 3 � 4 � 24.

213

73

�2.34 � 105

213

� �32 � 42


Figure IV.10: Complex number calculations

The TI-89 can also solve for the real and complex solutions of an equation. This is done by using the cSolve( function which is found in the Algebra sub-menu of the MATH menu.

The format of cSolve ( is cSolve(expression, variable). For example, to find the zeros ofpress 2nd MATH 9 [Algebra] alpha A [Complex] 1 [cSolve( ]. To complete

the computation, press X ^ 3 4 X ^ 2 + 14 X 20 0 , X) ENTER. The TI-89 will display real andcomplex solutions of the equation, as shown in Figure IV.11.

Figure IV.11: cSolve function

Note that this calculation and the answer are too long for both the entry line and the history area. You canscroll through the entire calculation or answer by using or to put the cursor on the appropriate lineand then using or to move the cursor to the part of the calculation or answer that you wish to see.

IV.2 Functions and Graphs

IV.2.1 Evaluating Functions: Suppose you receive a monthly salary of $1975 plus a commission of 10%of sales. Let your sales in dollars; then your wages in dollars are given by the equation

If your January sales were $2230 and your February sales were $1865, what was yourincome during those months?

Here’s one method to use your TI-89 to perform this task. Press Y= (above F1 key) or APPS 2 [Y= Editor] to display the function editing screen (Figure IV.12). You may enter as many as 99 differentfunctions for the TI-89 to use at one time. If there is already a function y1, press or as many timesas necessary to move the cursor to y1 and then press CLEAR to delete whatever was there. Then enter theexpression by pressing these keys: 1975 + .10 X ENTER. Now press HOME.1975 � .10x

W � 1975 � .10x.Wx �

��f�x� � x3 � 4x2 � 14x � 20,


Figure IV.12: Y= screen Figure IV.13: Evaluating a function

Assign the value 2230 to the variable by using these keystrokes (see Figure IV.13): 2230 STO XENTER. Then press the following keystrokes to evaluate y1 and find January’s wages: Y 1 ( X ) ENTER,completes the calculation. It is not necessary to repeat all these steps to find the February wages. Simplypress to begin editing the previous entry, change X to 1865, and press ENTER (see Figure IV.13).

You may also have TI-89 make a table of values for the function. Press TblSet to set up the table (FigureIV.14). Move the blinking cursor down to the fourth line beside Independent, then press and 2 [ASK]ENTER. This configuration permits you to input values for one at a time. Now press TABLE or APPS5 [Table], enter 2230 in the column, and press ENTER (see Figure IV.15). Press to move to the nextline and continue to enter additional values for The TI-89 automatically completes the table with the cor-responding values of y1. Press 2nd QUIT to leave the TABLE screen.

Figure IV.14: TABLE SETUP screen Figure IV.15: Table of values

Technology Tip: The TI-89 requires multiplication to be expressed between variables, so does not meanrather it is a new variable named So, you must use either ’s between the ’s or ^ for powers of

Of course, expressed multiplication is not required between a constant and a variable. See your TI-89 manualfor more information about the allowed usage of implied multiplication.

IV.2.2 Functions in a Graph Window: Once you have entered a function in the Y= screen of the TI-89,just press GRAPH to see its graph. The ability to draw a graph contributes substantially to our abilityto solve problems.

For example, here is how to graph First press Y= and delete anything that may be thereby moving with the arrow keys to y1 or to any of the other lines and pressing CLEAR wherever necessary.Then, with the cursor on the (now cleared) top line (y1), press (-) X ^ 3 + 4 X ENTER to enter the function(as in Figure IV.16). Now press GRAPH and the TI-89 changes to a window with the graph of (Figure IV.18).

While the TI-89 is calculating coordinates for a plot, it displays the word BUSY on the status line.

y � �x3 � 4x

y � �x3 � 4x.

x.x�xxx.x3,xxx

x.x

x

�x


Technology Tip: If you would like to see a function in the Y= menu and its graph in a graph window, bothat the same time, press MODE to open the MODE menu and press F2 to go to the second page. The cursor will be next to Split Screen. Select either TOP-BOTTOM or LEFT-RIGHT by pressing and 2 or 3,respectively. Now the 2 lines below the Split 1 App line have become readable, because these options applyonly when the calculator is in the split screen mode. The Split 1 App will automatically be the screen youwere on prior to pressing MODE. You can choose what you want the top or left-hand screen to show bymoving down to the Split 1 App line, pressing and the number of the application you want in that window.The Split 2 App determines what is shown in the bottom or right-hand window. Press ENTER to confirmyour choices and your TI-89’s screen will now be divided either horizontally or vertically (as you choose).Figure IV.16 show the graph and the Y= screen with the settings shown in Figure IV.17. The split screen isalso useful when you need to do some calculations as you trace along a graph. In split screen mode, one sideof the screen will be more heavily outlined. This is the active screen, i.e., the screen that you can currentlymodify. You can change which side is active by using 2nd to access the symbol above the APPS key. Fornow, restore the TI-89 to Full screen.

Technology Tip: Note that if you set one part of your screen to contain a table and the other to contain agraph, the table will not necessarily correspond to the graph unless you use TblSet to generate a newtable based on the functions being graphed (as in Section IV.2.1).

Figure IV.16: Split screen: LEFT-RIGHT Figure IV.17: MODE settings for Figure IV.16

Your graph window may look like the one in Figure IV.18 or it may be different. Because the graph ofextends infinitely far left and right and also infinitely far up and down, the TI-89 can display

only a piece of the actual graph. This displayed rectangular part is called a viewing window. You can easilychange the viewing window to enhance your investigation of a graph.

Figure IV.18: Graph of

The viewing window in Figure IV.18 shows the part of the graph that extends horizontally from to 10and vertically from to 10. Press WINDOW to see information about your viewing window. FigureIV.19 shows the WINDOW screen that corresponds to the viewing window in Figure IV.18. This is thestandard viewing window for the TI-89.

�10�10

y � �x3 � 4x

10

−10

−10 10

y � �x3 � 4x


The variables xmin and xmax are the minimum and maximum values of the viewing window; ymin andymax are the minimum and maximum values.

xscl and yscl set the spacing between the tick marks on the axes.

xres sets pixel resolution (1 through 10) for function graphs.

Figure IV.19: Standard WINDOW

Technology Tip: Small xres values improve graph resolution, but may cause the TI-89 to draw graphs moreslowly.

Use and to move up and down from one line to another in this list; pressing the ENTER key willmove down the list. Press CLEAR to delete the current value and then enter a new value. You may also editthe entry as you would edit an expression. Remember that a minimum must be less than the correspondingmaximum or the TI-89 will issue an error message. Also, remember to use the (-) key, not (which issubtraction), when you want to enter a negative value. Figures IV.18-19, IV.20-21, and IV.22-23 showdifferent WINDOW screens and the corresponding viewing window for each one.

Figure IV.20: Square WINDOW Figure IV.21: Graph of

To initialize the viewing window quickly to the standard viewing window (Figure IV.19), press F2 [Zoom]6 [ZoomStd]. To set the viewing window quickly to a square window (Figure IV.20), press F2 5[ZoomSqr]. More information about square windows is presented later in Section IV.2.4.

y � �x3 � 4x

10

−10

−20.8 20.8

�

y-x-


Figure IV.22: Custom WINDOW Figure IV.23: Graph of

Sometimes you may wish to display grid points corresponding to tick marks on the axes. This and othergraph format options may be changed while you are viewing the graph by pressing F1 to get the Tools menu(Figure IV.24) and then pressing 9 [Format] to display the Format menu (Figure IV.25) or by pressing |as indicated on the Tools menu in Figure IV.24. Move the blinking cursor to Grid; press 2 [ON] ENTERto redraw the graph. Figure IV.26 shows the same graph as in Figure IV.23 but with the grid turned on.

Figure IV.24: Tools menu Figure IV.25: Format menu

Figure IV.26: Grid turned on for

In general, you’ll want the grid turned off, so do that now by pressing and turning the Grid option toOFF, then pressing ENTER.

IV.2.3 Graphing Step and Piecewise-Defined Functions: The greatest integer function, written givesthe greatest integer less than or equal to a number On the TI-89, the greatest integer function is calledfloor( and is located under the Number sub-menu of the MATH menu (Figures IV.8-9). So, calculate

by pressing 2nd MATH 1 6 [floor(] 6.78 ) ENTER.

To graph go into the Y= menu, move beside y1 and press CLEAR 2nd MATH 1 6 X ) ENTERGRAPH. Figure IV.27 show this graph in a viewing window from to 5 in both directions.�5

y � �x,

� 6�6.78

x.�x,

y � �x3 � 4x

10

−10

−3 3

y � x3 � 4x

10

−10

−3 3


The true graph of the greatest integer function is a step graph, like the one in Figure IV.28. For the graph ofa segment should not be drawn between every pair of successive points. You can change this graph

from a Line to a Dot graph on the TI-89 by going to the Y= screen, moving the cursor up until this functionis selected (highlighted) and then pressing 2nd F6 [Style]. This opens the Graph Style menu. Move thecursor down to the second line and press ENTER or press 2; to have the selected graph plotted in Dot style.Now press GRAPH to see the result.

Figure IV.27: Line graph of Figure IV.28: Dot graph of

Technology Tip: When graphing functions in the Dot style, it improves the appearance of the graph to setxres to 1. Figure IV.28 was graphed with xres Also, the default graph style is Line, so you have to setthe style to Dot each time you wish to graph a function in Dot mode.

The TI-89 can graph piecewise-defined functions by using the when( function. The when( function is noton any of the keys but can be found in the CATALOG or typed from the keys. The format of the when(function is when(condition, trueResult, falseResult, unknownResult) where the falseResult andunknownResult are optional arguments.

For example, to graph the function (using Dot graph), you want to graph

when the condition is true and graph when the condition is false. First, clear any existingfunctions in the Y= screen. Then move to the y1 line and press 2nd a-lock W H E N alpha ( X 2nd <0 , X ^ 2 + 2 , X 1 ) ENTER (Figure IV.29). Then press GRAPH to display the graph. FigureIV.30 shows this graph in a viewing window from to 5 in both directions. This was done in Dot style,because the TI-89 will (incorrectly) connect the two sides of the graph at if the function is graphedin Line style.

Figure IV.29: Piecewise-defined function Figure IV.30: Piecewise-defined graph

Other test functions, such as and as well as logic operators can be found on the Test sub-menu ofthe MATH menu.

≥,≤,

5

−5

−5 5

x � 0�5

�

x � 1x < 0

x2 � 2f �x� � �x2 � 2,x � 1,

x < 0x ≥ 0

� 1.

y � �xy � �x

5

−5

−5 5

5

−5

−5 5

y � �x,


IV.2.4 Graphing a Circle: Here is a useful technique for graphs that are not functions but can be “split” intoa top part and a bottom part, or into multiple parts. Suppose you wish to graph the circle whose equation is

First solve for and get an equation for the top semicircle, and for the bottomsemicircle, Then graph the two semicircles simultaneously.

Use the following keystrokes to draw the circle’s graph. First clear any existing functions on the Y= screen.Enter as y1 and as y2 (see Figure IV.31) by pressing 2nd 36 X ^ 2 ) ENTER(-) 2nd 36 X ^ 2 ) ENTER. Then press GRAPH to draw them both (Figure IV.32).

Figure IV.31: Two semicircles Figure IV.32: Circle’s graph – standard WINDOW

If your range was set to the standard viewing window, your graph would look like Figure IV.32. Now thisdoes not look like a circle, because the units along the axes are not the same. This is where the squareviewing window is important. Press F2 5 and see a graph that appears more circular.

Technology Tip: Another way to get a square graph is to change the range variables so that the value ofis approximately times For example, see the WINDOW in Figure IV.33 to

get the corresponding graph in Figure IV.34. This method works because the dimensions of the TI-89’sdisplay are such that the ratio of vertical to horizontal is approximately

Figure IV.33: Figure IV.34: A “square” circle

The two semicircles in Figure IV.34 do not connect because of an idiosyncrasy in the way the TI-89 plots a graph.

Back when you entered as y2, you could have entered -y1 as y2 and saved some keystrokes.Try this by going into the Y= screen and pressing to move the cursor up to y2. Then press CLEAR (-)Y 1 ( X ) ENTER. The graph should be as before.

��36 � x2

�19

39.5�

3879

verticalhorizontal

9.5

−9.5

−19.75 19.75

3879.

xmax � xmin.3879ymax � ymin

10

−10

−10 10

�� 36 � x2�36 � x2

y � ��36 � x2.y � �36 � x2,yx2 � y2 � 36.


IV.2.5 Trace: Graph the function from Section IV.2.2 using the standard viewing window.(Remember to clear any other functions in the Y= screen.) Press any of the cursor directions and see the cursor move from the center of the viewing window. The coordinates of the cursor’s location aredisplayed at the bottom of the screen, as in Figure IV.35, in floating decimal format. This cursor is called afree-moving cursor because it can move from dot to dot anywhere in the graph window.

Remove the free-moving cursor and its coordinates from the window by pressing GRAPH, CLEAR,ESC, or ENTER. Press the cursor directions again and the free-moving cursor will reappear at the samepoint you left it.

Figure IV.35: Free-moving cursor

Press F3 [Trace] to enable the left and right directions to move the cursor from point to point along thegraph of the function. The cursor is no longer free-moving, but is now constrained to the function. Thecoordinates that are displayed belong to points on the function’s graph, so the coordinate is the calculatedvalue of the function at the corresponding coordinate (Figure IV.36).

Figure IV.36: Trace

Figure IV.37: Two functions Figure IV.38: and y � �.25xy � �x3 � 4x

10

−10

−10 10

10

−10

−10 10

x-y-

10

−10

−10 10

y � �x3 � 4x


Now plot a second function, along with Press Y= and enter for y2,then press GRAPH to see both functions.

Notice that in Figure IV.37 there are checkmarks ✓ to the left of both y1 and y2. This me that both functionswill be graphed, as shown in Figure IV.38. In the Y= screen, move the cursor onto y1 and press F4 [✓]. Thecheckmark left of y1 should disappear (Figure IV.39). Now press GRAPH and see that only y2 is plotted(Figure IV.40).

Figure IV.39: Only y2 active Figure IV.40: Graph of

Many different functions can be stored in the Y= list and any combination of them may be graphedsimultaneously. You can make a function active or inactive for graphing by pressing F4 when the function ishighlighted to add a checkmark (activate) or remove the checkmark (deactivate). Now go back to the Y=screen and do what is needed in order to graph y1 but not y2.

Now activate both functions so that both graphs are plotted. Press F3 and the cursor appears first on thegraph of because it is higher up on the Y= list. You know that the cursor is on this function,y1, because of the numeral 1 that is displayed in the upper right corner of the screen. Press the up ordown direction to move the cursor vertically to the graph of Now the numeral 2 is displayedin the upper right corner of the screen. Next press the left and right arrow keys to trace along the graph of

When more than one function is plotted, you can move the trace cursor vertically from one graphto another with the and directions.

Technology Tip: Trace along the graph of and press and hold either the or direction. Thecursor becomes larger and pulses as it moves along the graph. Eventually you will reach the left or right edgeof the window. Keep pressing the direction and the TI-89 will allow you to continue to trace by panning theviewing window. Check the WINDOW screen to see that the xmin and xmax are automatically updated.

If you trace along the graph of the cursor will eventually move above or below the viewingwindow. The cursor’s coordinates on the graph will still be displayed, though the cursor itself can no longerbe seen. When you are tracing along a graph, press ENTER and the window will quickly pan over so thatthe cursor’s position on the function is centered in a new viewing window. This feature is especially helpfulwhen you trace near or beyond the edge of the current viewing window.

The TI-89’s display has 159 horizontal columns of pixels and 99 vertical rows. So, when you trace a curveacross a graph window, you are actually moving from xmin to xmax in 158 equal jumps, each called You

would calculate the size of each jump to be Sometimes you may want the jumps to be

friendly numbers like 0.1 or 0.25 so that, when you trace along the curve, the coordinates will beincremented by such a convenient amount. Just set your viewing window for a particular increment

by making For example, if you want xmin and 0.3, setLikewise, set if you want the vertical

increment to be some special y. xmax � xmin � 98 � y.xmax � �5 � 158 � 0.3 � 42.4.

x ��5�xmax � xmin � 158 � x.x

x-

x �xmax � xmin

158.

x.

y � �x3 � 4x,

y � �.25x

y � �.25x.

y � �.25x.

y � �x3 � 4x

y � �.25x

10

−10

−10 10

�.25xy � �x3 � 4x.y � �.25x,


To center your window around a particular point, say and also have a certain setand make Likewise, make and makeFor example, to center a window around the origin with both horizontal and

vertical increments of 0.25, set the range so that and

See the benefit by first graphing in a standard viewing window. Trace near its intercept,which is and move towards its intercept, which is Then press F2 4 [ZoomDec] and traceagain near the intercepts.

IV.2.6 Zoom: Plot again the two graphs for and There appears to be anintersection near The TI-89 provides several ways to enlarge the view around this point. You canchange the viewing window directly by pressing WINDOW and editing the values of xmin, xmax, ymin,and ymax. Figure IV.42 shows a new viewing window for the range displayed in Figure IV.41. The cursorhas been moved near the point of intersection; move your cursor closer to get the best approximation possiblefor the coordinates of the intersection.

Figure IV.41: New WINDOW Figure IV.42: Closer view

A more efficient method for enlarging the view is to draw a new viewing window with the cursor. Start againwith a graph of the two functions and in a standard viewing window (press F2 6for the standard viewing window).

Now imagine a small rectangular box around the intersection point, near Press F2 1 [ZoomBox](Figure IV.43) to draw a box to define this new viewing window. Use the arrow keys to move the cursor,whose coordinates are displayed at the bottom of the window, to one corner of the new viewing window youimagine.

Press ENTER to fix the corner where you moved the cursor; it changes shape and becomes a blinking square(Figure IV.44). Use the arrow keys again to move the cursor to the diagonally opposite corner of the newwindow (Figure IV.45). Note that you can press and hold or with or for this. If this box looksall right to you, press ENTER. The rectangular area you have enclosed will now enlarge to fill the graphwindow (Figure IV.46).

x � 2.

y � �.25xy � �x3 � 4x

2.5

−2.5

1.5 2.5

x � 2.y � �.25x.y � �x3 � 4x

��1, 0�.x-�0, 1�,y-y � x2 � 2x � 1

ymax � 0 � 49 � 0.25 � 12.25.ymin � 0 � 49 � 0.25 � �12.25,� 19.75,xmax � 0 � 79 � 0.25xmin � 0 � 79 � 0.25 � �19.75,

�0, 0�,ymax � k � 49 � y.ymin � k � 49 � yxmax � h � 79 � x.xmin � h � 79 � x

x,�h, k),


Figure IV.43: Zoom menu Figure IV.44: One corner selected

You may cancel the zoom any time before you press this last ENTER. Press F2 once more and start over.Press ESC or GRAPH to cancel the zoom, or press 2nd QUIT to cancel the zoom and return to thehome screen.

Figure IV.45: Box drawn Figure IV.46: New viewing window

You can also quickly magnify a graph around the cursor’s location. Return once more to the standard viewingwindow for the graph of the two functions and Press F2 2 [ZoomIn] and thenmove the cursor as close as you can to the point of intersection near (see Figure IV.47). Then pressENTER and the calculator draws a magnified graph, centered at the cursor’s position (Figure IV.48). Therange variables are changed to reflect this new viewing window. Look in the WINDOW menu to verify this.

Figure IV.47: Before a zoom in Figure IV.48: After a zoom in

As you see in the Zoom menu (Figure IV.43), the TI-89 can zoom in (press F2 2) or zoom out (press F2 3).Zoom out to see a larger view of the graph, centered at the cursor position. You can change the horizontaland vertical scale of the magnification by pressing F2 alpha C [SetFactors...] (see Figure IV.49) andediting xFact and yFact, the horizontal and vertical magnification factors. (The zFact is only used whendealing with three-dimensional graphs.)

1.97

−3.03

−0.47 4.52

10

−10

−10 10

x � 2y � �.25x.y � �x3 � 4x

0.79

−1.32

1.39 2.78

10

−10

−10 10

10

−10

−10 10


Figure IV.49: ZOOM FACTORS menu

The default zoom factor is 4 in both directions. It is not necessary for xFact and yFact to be equal.Sometimes, you may prefer to zoom in one direction only, so the other factor should be set to 1. Press ESCto leave the ZOOM FACTORS menu and go back to the graph. (Pressing 2nd QUIT will take you back tothe home screen.)

Technology Tip: The TI-89 remembers the window it displayed before a zoom. So, if you should zoom intoo much and lose the curve, press F2 alpha B [Memory] 1 [ZoomPrev] to go back to the window before.If you want to execute a series of zooms but then return to a particular window, press F2 alpha B 2[ZoomSto] to store the current window’s dimensions. Later, press F2 alpha B 3 [ZoomRcl ] to recall thestored window.

IV.2.7 Value: Graph in the standard viewing window (Figure IV.18). The TI-89 can calcu-late the value of this function for any given (between the xmin and xmax values).

Press F5 [Math] to display the Math menu (see Figure IV.50), then press 1 [Value]. The graph of thefunction is displayed and you are prompted to enter a value for Press 1 ENTER. The value you enteredand its corresponding value are shown at the bottom of the screen and the cursor is located at the point

on the graph (see Figure IV.51).

Figure IV.50: Math menu Figure IV.51: Finding a value

Note that if you have more than one graph on the screen, the upper left corner of the TI-89 screen will displaythe numeral corresponding to the equation of the function in the Y= list whose value is being calculated.Press or to move the cursor vertically between functions at the entered value.

IV.2.8 Relative Minimums and Maximums: Graph once again in the standard viewingwindow. This function appears to have a relative minimum near and a relative maximum near You may zoom and trace to approximate these extreme values.

x � 1.x � �1y � �x3 � 4x

x-

10

−10

−10 10

�1, 3�y-

x-x.

xy � �x3 � 4x


First trace along the curve near the relative minimum. Notice by how much the values and values changeas you move from point to point. Trace along the curve until the coordinate is as small as you can get it,so that you are as close as possible to the relative minimum, and zoom in (press F2 2 ENTER or use a zoombox). Now trace again along the curve and, as you move from point to point, see that the coordinates changeby smaller amounts than before. Keep zooming and tracing until you find the coordinates of the relativeminimum point as accurately as you need them, approximately

Follow a similar procedure to find the relative maximum. Trace along the curve until the coordinate is asgreat as you can get it, so that you are as close as possible to the relative maximum, and zoom in. The relativemaximum point on the graph of is approximately

The TI-89 can automatically find the relative maximum and relative minimum points. While viewing thegraph, press F5 to display the Math menu (Figure IV.50). Choose 3 [Minimum] to calculate the minimumvalue of the function and 4 [Maximum] for the maximum. You will be prompted to trace the cursor alongthe graph first to a point left of the minimum/maximum (press ENTER to set this lower bound). Note thearrow near the top of the display marking the lower bound (as in Figure IV.52).

Figure IV.52: Finding a minimum Figure IV.53: Relative minimum on

Now move to a point right of the minimum/maximum and set an upper bound by pressing ENTER. Thecoordinates of the relative minimum/maximum point will be displayed (see Figure IV.53). Good choices forthe lower and upper bounds can help the TI-89 work more efficiently and quickly.

Note that if you have more than one graph on the screen, the upper right corner of the TI-89 screen will showthe number of the function whose minimum/maximum is being calculated.

IV.2.9 Inverse Functions: The TI-89 draws the inverse function of a one-to-one function. Graph as y1 in the standard viewing window (see Figure IV.54). Next, press 2nd F6 [Draw] to display the Drawmenu (see Figure IV.55), then press 3 [DrawInv]. You are automatically returned to the home screen. PressX ^ 3 + 1 ENTER (see Figure IV.56). These keystrokes instruct the TI-89 to draw the inverse function of

The original function and its inverse function will be displayed (see Figure IV.57). Note that thecalculator must be in function mode in order to use DrawInv.

To clear the graph of the inverse function, press 2nd F6 1 [ClrDraw].

y � x3 � 1.

y � x3 � 1

y � �x3 � 4x

10

−10

−10 10

10

−10

−10 10

�1.15, 3.08�.y � �x3 � 4x

y-

��1.15, �3.08�.

y-y-x-


Figure IV.54: Graph of Figure IV.55: Draw menu

Figure IV.56: DrawInv Figure IV.57: Graph of and its inverse function

IV.2.10 Tangent Lines: Once again, graph in the standard viewing window (see Figure IV.54).The TI-89 can draw the tangent line to a graph of a function at a specified point.

Press F5 alpha A [Tangent]. You are prompted to enter a value for So, press or to select a point orenter a value for (see Figure IV.58). Press 1 ENTER. The graph of the original function and the tangentline to the graph at will be displayed (see Figure IV.59). Note that the equation of the tangent line isdisplayed at the bottom of the screen.

To clear the tangent line, press 2nd F6 1.

Figure IV.58: Tangent Figure IV.59: Graph of and tangent line at x � 1

y � x3 � 1

10

−10

−10 10

10

−10

−10 10

x � 1x

x.

y � x3 � 1

y � x3 � 1

10

−10

−10 10

y � x3 � 1

10

−10

−10 10


IV.3 Solving Equations and Inequalities

IV.3.1 Intercepts and Intersections: Tracing and zooming are also used to locate an intercept of a graph,where a curve crosses the axis. For example, the graph of crosses the axis three times (seeFigure IV.60). After tracing over to the intercept point that is farthest to the left, zoom in (Figure IV.61).Continue this process until you have located all three intercepts with as much accuracy as you need. Thethree intercepts of are approximately 2.828, 0, and 2.828.

Figure IV.60: Graph of Figure IV.61: Near an intercept of

Technology Tip: As you zoom in, you may also wish to change the spacing between tick marks on the axis so that the viewing window shows scale marks near the intercept point. Then the accuracy of your

approximation will be such that the error is less than the distance between two tick marks. Change the scale on the TI-89 from the WINDOW menu. Move the cursor down to xscl and enter an appropriate value.

The intercept of a function’s graph is a zero of the function, so while viewing the graph, press F5 (FigureIV.50) and choose 2 [Zero] to find a zero of this function. Set a lower bound and upper bound as describedin Section IV.2.8. The TI-89 shows the coordinates of the point and indicates that it is a zero (Figure IV.62).

Figure IV.62: A zero of

Trace and Zoom are especially important for locating the intersection points of two graphs, say the graphsof and Trace along one of the graphs until you arrive close to an intersectionpoint. Then press or to jump to the other graph. Notice that the coordinate does not change, but the

coordinate is likely to be different (Figures IV.63 and IV.64).y-x-

y � �.25x.y � �x3 � 4x

y � x3 � 8x

10

−10

−10 10

x-

x-

x-

y � x3 � 8xx-y � x3 � 8x

2.5

−2.5

−5.41 −0.41

10

−10

−10 10

�y � x3 � 8xx-

x-x-y � x3 � 8xx-x-


Figure IV.63: Trace on Figure IV.64: Trace on

When the two coordinates are as close as they can get, you have come as close as you now can to the pointof intersection. So, zoom in around the intersection point, then trace again until the two coordinates are asclose as possible. Continue this process until you have located the point of intersection with as much accuracyas necessary. The points of intersection are approximately and

You can also find the point of intersection of two graphs by pressing F5 5 [Intersection]. Trace with thecursor first along one graph near the intersection and press ENTER; then trace with the cursor along theother graph and press ENTER. Marks are placed on the graphs at these points. Then set the lower andupper bounds for the coordinate of the intersection point and press ENTER again. Coordinates of theintersection will be displayed at the bottom of the window. More will be said about the Intersection featurein Section IV.3.3.

IV.3.2 Solving Equations by Graphing: Suppose you need to solve the equation First graph in a window large enough to exhibit all its intercepts, corresponding to all the equation’s real zeros (roots). Then use Zoom and Trace, or the TI-89’s zero finder,to locate each one. In fact, this equation has just one real solution,

Remember that when an equation has more than one intercept, it may be necessary to change the viewingwindow a few times to locate all of them.

The TI-89 has a solve( function. To use this function, you must be in the home screen. To solve the equationpress 2nd MATH 9 1 [solve(] 24 X ^ 3 36 X + 17 = 0 , X ) ENTER. The

TI-89 displays the value of the zero (Figure IV.65). Note that any letter could have been used for the variable.This is the reason that you must indicate to the TI-89 that the variable being used is X.

Figure IV.65: solve( function

Technology Tip: To solve an equation like you may first rewrite it in general form,and proceed as above. However, the solve( function does not require that the

function be in general form. You may also graph the two functions and then zoomand trace to locate their point of intersection.

y � 36x,y � 24x3 � 1724x3 � 36x � 17 � 0,

24x3 � 17 � 36x,

�24x3 � 36x � 17 � 0,

x-

x � �1.414.

x-y � 0 � 79 � 0.25 � �19.75,24x3 � 36x � 17 � 0.

x-

�

�2.062, �0.515�.�0, 0�,��2.062, 0.515�,

y-y-

y � �.25xy � �x3 � 4x

10

−10

−10 10

10

−10

−10 10


IV.3.3 Solving Systems by Graphing: The solutions to a system of equations correspond to the points ofintersection of their graphs (Figure IV.66). For example, to solve the system and first graph them together. Then use Zoom and Trace or the Intersection option in the Math menu, to locatetheir point of intersection, which is (see Figure IV.67).

Figure IV.66: Solving a system of equations Figure IV.67: The point of intersection is

The solutions of the system of two equations and correspond to the solutions ofthe single equation which simplifies to So, you may also graph

and find its intercept to solve the system or use the solve( function.

IV.3.4 Solving Inequalities by Graphing: Consider the inequality To solve it with your

TI-89, graph the two functions and (Figure IV.68). First locate their point of

intersection, at The inequality is true when the graph of lies above the graph of

and that occurs when So the solution is or

Figure IV.68: Solving

The TI-89 is capable of shading the region above or below a graph, or between two graphs. For example, tograph first enter the function as y1. Then, highlight y1 and press 2nd F6 7 [Above](see Figure IV.69). These keystrokes instruct the TI-89 to shade the region above Press

GRAPH to see the graph. The region above the graph will be shaded using the default shading optionof vertical lines, as in Figure IV.70.

y � x2 � 1.y � x2 � 1y ≥ x2 � 1,

1 �3x2≥ x � 4

10

−10

−10 10

��, 2�.x ≤ 2,x < 2.y � x � 4,

y � 1 �3x2

x � 2.

y � x � 4y � 1 �3x2

1 �3x2≥ x � 4.

x-y � 4x � 44x � 4 � 0.2x � 5 � �2x � 1,

y � �2x � 1y � 2x � 5

��1, 3�.

10

−10

−10 10

10

−10

−10 10

��1, 3�

y � �2x � 1,y � 2x � 5


Figure IV.69: Shade Above style Figure IV.70 Graph of

Now use shading to solve the previous inequality, The solution is the region which is below

the graph of and above First graph both equations. Then, from the graph screen,

press F5 alpha C [Shade]. The TI-89 will prompt for the function that you want to have the shading above.Use or to move the cursor to the graph of then press ENTER. The TI-89 will then promptfor the function that you want to have the shading below, so use or to move the cursor to the graph

of and press ENTER. The TI-89 will then prompt for the lower bound then the upper bound,

which are the left and right edges, respectively, of the extent of the shading. If you do not enter a lower orupper bound, the values of xmin and xmax will be used. So, in this case, press ENTER twice to set the

lower and upper bounds. The shaded area extends left from so the solution to is

or (see Figure IV.71).

Figure IV.71: Graph of

IV.4 Trigonometry

IV.4.1 Degrees and Radians: The trigonometric functions can be applied to angles measured either inradians or degrees, but you should take care that the TI-89 is configured for whichever measure you need.Press MODE to see the current settings. Press three times and move down to the fourth line of the firstpage of the MODE menu where angle measure is selected. Then press to display the options. Use or

to move from one option to the other. Either press the number corresponding to the measure or, whenthe measure is highlighted, press ENTER to select it. Then press ENTER to confirm your selection andleave the MODE menu.

1 �3x2≥ x � 4

10

−10

−10 10

��, 2�x ≤ 2,

1 �3x2≥ x � 4x � 2,

y � x � 4,

y � x � 4,

y � x � 4,y � 1 �3x2

1 �3x2≥ x � 4.

y ≥ x2 � 1

10

−10

−10 10


It’s a good idea to check the angle measure setting before executing a calculation that depends on a particu-lar measure. You may change a mode setting at any time and not interfere with pending calculations. Fromthe home screen, try the following keystrokes to see this in actions


MODE ENTERENTER 2nd SIN 45 ) ENTER .7071067812

2nd SIN 2nd ) ENTER .0548036651

MODE ENTERENTER 2nd SIN 2nd ) ENTER 0

2nd SIN 45 ) ENTER .8509035245

2nd SIN 2nd 6 ) ENTER .5

The first line of keystrokes sets the TI-89 in degree mode and calculates the sine of 45 degrees. While thecalculator is still in degree mode, the second line of keystrokes calculates the sine of degrees, approximately3.1415 The third line changes to radian mode just before calculating the sine of radians. The fourth line

calculates the sine of 45 radians. Finally, the fifth line calculates the sine of radians (the calculator remains

in radian mode).

The TI-89 makes it possible to mix degrees and radians in a calculation. Execute these keystrokes to calculate

as shown in Figure IV.72: 2nd TAN 45 2nd MATH 2 [Angle] 1 [ ] ) + 2nd SIN 2nd

6 ) 2nd MATH 2 2 [ ] ENTER. Do you get 1.5 whether your calculator is in either degree mode or inradian mode?

The degree sign can also be entered by pressing 2nd which saves keystrokes. There is no correspondingkey for the radian symbol.

Figure IV.72: Angle measure

Technology Tip: The automatic left parenthesis that the TI-89 places after functions such as sine, cosine,and tangent (as noted in Section IV.1.3) can affect the outcome of calculations. In the previous example, thedegree sign must be inside of the parentheses so that when the TI-89 is in radian mode, it calculates thetangent of 45 degrees, rather than converting the tangent of 45 radians into an equivalent number of degrees.

Also, the parentheses around the fraction are required so that when the TI-89 is in radian mode, it converts

into radians rather than converting merely the 6 to radians. Experiment with the placement of parentheses

to see how they affect the result of computation.

�

6

�

6

,

r� �

�tan 45� � sin �

6

�

6

��.�

� �sin �

6

sin 45

�sin �

�sin ��

sin 45�


IV.4.2 Graphs of Trigonometric Functions: When you graph a trigonometric function, you need to paycareful attention to the choice of graph window and to your angle measure configuration. For example, graph

in the standard viewing window in radian mode. Trace along the curve to see where it is. Zoom

in to a better window, or use the period and amplitude to establish better WINDOW values.

Technology Tip: Because when in radian mode, set xmin and xmax to cover theinterval from 0 to

Next graph in the standard window, then press F2 7 [ZoomTrig] to change to a special window

for trigonometric functions in which the xscl is or and the vertical range is from to 4.

The TI-89 plots consecutive points and then connects them with a segment, so the graph is not exactly whatyou should expect. You may wish to change the plot style from Line to Dot (see Section IV.2.3) when youplot the tangent function.

IV.5 Scatter Plots

IV.5.1 Entering Data: The table shows the total prize money (in millions of dollars) awarded at theIndianapolis 500 race from 1996 to 2005. (Source: Indy Racing League)

We’ll now use the TI-89 to construct a scatter plot that represents these points and to find a linear model thatapproximates the given data.

The TI-89 holds data in lists. You can create as many list names as your TI-89 memory has space to store.Before entering this new data, clear the data in the lists that you want to use. To delete a list press 2ndVAR-LINK. This will display a list of folders showing the variables defined in each folder. Highlight thename of the list that you wish to delete and press F1 [Manage] 1 [Delete] ENTER.

Now press APPS 6 [Data/Matrix Editor] 3 [New...] P R I Z E ENTER to open a new variablecalled PRIZE (Figure IV.73). Press ENTER to then begin entering the variable values, with the years goingin column c1. Instead of entering the full year, let represent 1996, represent 1997, and so on.Here are the keystrokes for the first three years: 6 ENTER 7 ENTER 8 ENTER and so on, then press tomove to the next list. Move up to the first row and press 8.11 ENTER 8.61 ENTER 8.72 ENTER and soon (see Figure IV.74).

Figure IV.73: Entering a new variable Figure IV.74: Entering data points

x � 7x � 6

�490��

2� 1.5708

y � tan x

2�.� 6.3� 0� � 3.1,

y �sin 30x

30


Year 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

Prize (in millions) $8.11 $8.61 $8.72 $9.05 $9.48 $9.61 $10.03 $10.15 $10.25 $10.30

You may edit statistical data in almost the same way you edit expressions in the home screen. To insert ordelete a data point, move the cursor over the data point (cell) you wish to add or delete. will delete theentire cell, not just the character or value to the left of the cursor. So, move the cursor to any value you wishto change, then type the correction. To insert a cell, move to the cell below the place where you want to insertthe new cell and press 2nd F6 [Util ] 1 [Insert] 1 [cell ] and a new empty cell is open.

IV.5.2 Plotting Data: First check the MODE screen (Figure IV.1) to make sure that you are in FUNCTIONgraphing mode. With the data points showing, press F2 [Plot Setup] to display the Plot Setup screen. If noother plots have been entered, Plot 1 is highlighted by default. Press F1 [Define] to select the options forthe plot. Use , , and ENTER to select the Plot Type as Scatter and the Mark as a Box. Press C alpha1 to set the independent variable, and press alpha C 2 to set the dependent variable, as shown in FigureIV.75, then press ENTER to save the options and press GRAPH to graph the data points. (Make surethat you have cleared or turned off any functions in the Y= screen, or those functions will be graphedsimultaneously.) Figure IV.76 shows this plot in a window from 0 to 16 horizontally and vertically. You maynow press F3 [Trace] to move from data point to data point.

Figure IV.75: Plot 1 menu Figure IV.76: Scatter plot

To draw the scatter plot in a window adjusted automatically to include all the data you entered, press F2 9[ZoomData].

When you no longer want to see the scatter plot press APPS 6 1 [Current] F2, highlight Plot 1 and use F4 [✓] to deselect Plot 1 or press Y=, move the cursor up to highlight Plot 1, and press F4 [✓]. TheTI-89 still retains all the data you entered.

IV.5.3 Regression Line: The TI-89 calculates slope and intercept for the line that best fits all the data.After the data points have been entered, while still in the Data/Matrix Editor, press F5 [Calc]. For theCalculation Type, choose 5 [LinReg] and set the x variable to c1 and the y variable to c2. In order to havethe TI-89 graph the regression equation, set Store RegEQ to as y1(x) as shown in Figure IV.77. PressENTER and the TI-89 will calculate a linear regression model with the slope named a and the interceptnamed b (Figure IV.78). The correlation coefficient (corr) measures how well the linear regression equationfits with the data. The closer the absolute value of the correlation coefficient is to 1, the better the fit; thecloser the absolute value of the correlation coefficient is to 0, the worse the fit. The TI-89 displays both thecorrelation coefficient and the coefficient of determination �R2�.

y-

y-

16

0

0 16

y,x,


Figure IV.77: Linear regression: Figure IV.78: Linear regression modelCalculate dialog box

Press ENTER to accept the regression equation and close the STAT VARS screen. To see both the datapoints and the regression line (Figure IV.79), go to the Plot Setup screen and select Plot 1, then press

GRAPH to display the graph.

Figure IV.79: Linear regression line

IV.5.4 Other Regression Models: After data points have been entered, you can choose from nine differentregression models. They are all located in the Calc menu of the Data/Matrix Editor.

IV.6 Box-and-Whisker Plots

IV.6.1 Entering Data: The list shows the land and water area (in thousands of square miles) of the 50 states.(Source: U.S. Census Bureau)

Alabama 52.4 Louisiana 51.8 Ohio 44.8Alaska 663.3 Maine 35.4 Oklahoma 69.9Arizona 114.0 Maryland 12.4 Oregon 98.4Arkansas 53.2 Massachusetts 10.6 Pennsylvania 46.1California 163.7 Michigan 96.7 Rhode Island 1.5Colorado 104.1 Minnesota 86.9 South Carolina 32.0Connecticut 5.5 Mississippi 48.4 South Dakota 77.1Delaware 2.5 Missouri 69.7 Tennessee 42.1Florida 65.8 Montana 147.0 Texas 268.6Georgia 59.4 Nebraska 77.4 Utah 84.9Hawaii 10.9 Nevada 110.6 Vermont 9.6Idaho 83.6 New Hampshire 9.4 Virginia 42.8Illinois 57.9 New Jersey 8.7 Washington 71.3Indiana 36.4 New Mexico 121.6 West Virginia 24.2Iowa 56.3 New York 54.6 Wisconsin 65.5Kansas 82.3 North Carolina 53.8 Wyoming 97.8Kentucky 40.4 North Dakota 70.7

16

0

0 16


We’ll now use the TI-89 to construct a box-and-whisker plot that represents the data and finds the smallestnumber, the lower quartile, the median, the upper quartile, and the largest number.

The TI-89 holds data in lists. You can create as many list names as your TI-89 memory has space to store.Before entering this new data, clear the data in the lists that you want to use. To delete a list press 2nd VAR-LINK. This will display a list of folders showing the variables defined in each folder. Highlight thename of the list that you wish to delete and press F1 [Manage] 1 [Delete] ENTER.

Now press APPS 6 [Data/Matrix Editor] 3 [New . . .] A R E A ENTER to open a new variablecalled AREA (Figure IV.80). Press ENTER to then begin entering the variable values, with the values goingin column c1. Here are the keystrokes for the first three states: 52.4 ENTER 663.3 ENTER 114.0 ENTERand so on (see Figure IV.81).

Figure IV.80: Entering a new variable Figure IV.81: Entering data

You may edit statistical data in almost the same way you edit expressions in the home screen. To insert ordelete a value, move the cursor over the value (cell) you wish to add or delete. will delete the entire cell,not just the character or value to the left of the cursor. So, move the cursor to any value you wish to change,then type the correction. To insert a cell, move to the cell below the place where you want to insert the newcell and press 2nd F6 [Util] 1 [Insert] 1 [cell] and a new empty cell is open.

IV.6.2 Plotting Data: First check the MODE screen (Figure IV.1) to make sure that you are in FUNCTIONgraphing mode. With the data showing, press F2 [Plot Setup] to display the Plot Setup screen. If no otherplots have been entered, Plot 1 is highlighted by default. Press F1 [Define] to select the options for the plot.Use 3 to select the Plot Type as Box Plot. Press C alpha 1 ENTER to set the independent variable,

as shown in Figure IV.82, then press ENTER to save the options and press F2 [WINDOW] F2 [Zoom]9 [ZoomData] to graph the box-and-whisker plot. (Make sure that you have cleared or turned off any func-tions in the Y= screen, or those functions will be graphed simultaneously.) Figure IV.83 shows the box-and-whisker plot in a window adjusted automatically to include all the data you entered. You may now press F3[Trace] and the left and right cursor keys to move between minX (the smallest number), q1 (the lower quar-tile), Med (the median), q3 (the upper quartile), and maxX (the largest number) as shown in Figure IV.83.

Figure IV.82: Plot 1 menu Figure IV.83: Box-and-whisker plot

When you no longer want to see the box-and-whisker plot press APPS 6 1 [Current] F2, highlight Plot 1and use F4 [✓] to deselect Plot 1 or press Y=, move the cursor up to highlight Plot 1, and press F4 [✓].The TI-89 still retains all the data you entered.

x,


IV.7 Matrices

IV.7.1 Making a Matrix: The TI-89 can display and use as many different matrices as the memory will hold.

Here’s how to store this matrix in your calculator.

From the home screen, press APPS 6 3. Set the Type to Matrix, the Variable to a (this is the “name” ofthe matrix), the Row dimension to 3 and the Col dimension to 4 (Figure IV.84). Press ENTER to acceptthese values.

Figure IV.84: Data/Matrix Editor Figure IV.85: Editing a matrix

The display will show the matrix as a grid with zeros in the rows and columns specified in the definition ofthe matrix.

Use the cursor pad or press ENTER repeatedly to move the cursor to a matrix element you want to change.If you press ENTER, you will move right across a row and then back to the first column of the next row.The lower left of the screen shows the cursor’s current location within the matrix. The element in the secondrow and first column in Figure IV.85 is highlighted, so the lower left of the window is r2c1 = -1 showingthat element’s current value. Enter all the elements of matrix a; pressing ENTER after entering each value.

When you are finished, leave the matrix editing screen by pressing 2nd QUIT or HOME to return to thehome screen.

IV.7.2 Matrix Math: From the home screen, you can perform many calculations with matrices. To seematrix a, press alpha A ENTER (Figure IV.86).

Perform the scalar multiplication 2a by pressing 2 alpha A ENTER. The resulting matrix is displayed onthe screen. To create matrix b as 2a press 2 alpha A STO alpha B ENTER (Figure IV.87), or if youdo this immediately after calculating 2a, press only STO alpha B ENTER. The calculator will displaythe matrix.

Figure IV.86: Matrix a Figure IV.87: Matrix b

To add two matrices, say a and b, create b (with the same dimensions as a) and then press alpha A + alphaB ENTER. Subtraction is performed in a similar manner.

�

�

1

�12

�23

�5

305

94

17�3 � 4


Now create a matrix called c with dimensions of and enter the matrix as c. For matrix

multiplication of c by a, press alpha C alpha A ENTER. If you tried to multiply a by c, your TI-89 wouldnotify you of an error because the dimensions of the two matrices do not permit multiplication in this way.

IV.7.3 Row Operations: Here are the keystrokes necessary to perform elementary row operations on amatrix. Your textbook provides a more careful explanation of the elementary row operations and their uses.

To interchange the second and third rows of the matrix that was defined in Figure IV.86, press 2nd MATH 4 [Matrix] alpha J [Row ops] 1 [rowSwap( ] alpha A , 2 , 3 ) ENTER (see Figure IV.88). The format ofthis command is rowSwap(matrix1, index1, index2).

To add row 2 and row 3 and store the results in row 3, press 2nd MATH 4 alpha J 2 [rowAdd( ] alpha A ,2 , 3 ) ENTER. The format of this command is rowAdd(matrix1, index1, index2).

To multiply row 2 by and store the results in row 2, thereby replacing row 2 with new values, press 2nd MATH 4 alpha J 3 [mRow(] (-) 4 , alpha A , 2 ) ENTER. The format of this command ismRow(expression, matrix1, index).

Figure IV.88: Interchange rows 2 and 3 Figure IV.89: Add times row 2 to row 3

To multiply row 2 by and add the results to row 3, thereby replacing row 3 with new values, press 2ndMATH 4 alpha J 4 [mRowAdd( ] (-) 4 , alpha A , 2 , 3 ) ENTER (see Figure IV.89). The format of thiscommand is mRowAdd(expression, matrix1, index1, index2).

Technology Tip: Note that your TI-89 does not store a matrix obtained as the result of any row operations.So, when you need to perform several row operations in succession, it is a good idea to store the result ofeach one in a temporary place.

For example, use row operations to solve this system of linear equations: .

First enter this augmented matrix as a in your TI-89: . Then return to the home

screen and store this matrix as e (press alpha A STO alpha E ENTER) so you may keep the original incase you need to recall it. Here are the row operations and their associated keystrokes. At each step, the resultis stored in e and replaces the previous matrix e. The last step of the row operations is shown in Figure IV.90.

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1

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�23

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305

9�417�

� x�x2x

�

�

�

2y3y5y

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�

3z

5z

�

�

�

9�417

�4

�4

�4,

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21

0�5

3�1�2 � 3


Row Operation Keystrokes

Add row 1 to row 2. 2nd MATH 4 alpha J 2 alpha E , 1 , 2 ) STO alpha E ENTER

Add times row 1 to row 3. 2nd MATH 4 alpha J 4 (-) 2 , alpha E , 1 , 3 ) STO alpha E ENTER

Add row 2 to row 3. 2nd MATH 4 alpha J 2 alpha E , 2 , 3 ) STOalpha E ENTER

Multiply row 3 by 2nd MATH 4 alpha J 3 1 2 , alpha E , 3 ) STOalpha E ENTER

Figure IV.90: Row-echelon form of matrix after row operations

So, and

Technology Tip: The TI-89 can produce a row-echelon form and the reduced row-echelon form of a matrix.The row-echelon form of matrix a is obtained by pressing 2nd MATH 4 3 [ref( ] alpha A ) ENTER (seeFigure IV.91) and the reduced row-echelon form is obtained by pressing 2nd MATH 4 4 [rref(] alpha AENTER (see Figure IV.92). Note that the row-echelon form of a matrix is not unique, so your calculator maynot get exactly the same matrix as you do by using row operations. However, the matrix that the TI-89produces will result in the same solution to the system.

Figure IV.91: Row-echelon form Figure IV.92: Reduced row-echelon form

IV.7.4 Determinants and Inverses: Enter this matrix as a: . Because this consists

of the first three columns of the matrix a that was previously used, you can go to the matrix, move the cursorinto the fourth column and press 2nd F6 [Util] 2 [Delete] 3 [column]. This will delete the column

that the cursor is in. To calculate its determinant go to the home screen and press 2nd

MATH 4 2 [det(] alpha A ) ENTER. You should find that the determinant is 2 as shown in Figure IV.93. 1�1

2

�23

�5

305

1�1

2

�23

�5

305�3 � 3

x � 1.y � �1,z � 2,

��12.

�

��2

�


Figure IV.93: and

Because the determinant of the matrix is not zero, it has an inverse matrix. Press alpha A ^ (-) 1 ENTER tocalculate the inverse of matrix a. The result is shown in Figure IV.93.

Now let’s solve a system of linear equations by matrix inversion. Once again, consider

. The coefficient matrix for this system is the matrix which was

entered as a in the previous example. Now enter the matrix as b. Because b was used before,

when we stored 2a as b, press APPS 6 2 [Open…] 2 [Matrix] and use to move the cursorto b, then press ENTER twice to go to the matrix previously saved as b, which can be edited. Return to thehome screen and press alpha A ^ (-) 1 alpha B ENTER to calculate the solution matrix (Figure IV.94).The solution is still and

Figure IV.94: Solution matrix

IV.8 Sequences and Sums

IV.8.1 Iteration with the ANS key: The ANS feature enables you to perform iteration, the process of

evaluating a function repeatedly. As an example, calculate for Then calculate for

the answer to the previous calculation. Continue to use each answer as in the next calculation. Hereare keystrokes to accomplish this iteration on the TI-89 calculator (see the results in Figure IV.95). Noticethat when you use ANS in place of in a formula, it is sufficient to press ENTER to continue an iteration.

Iteration Keystrokes Display

1 27 ENTER 27

2 ( 2nd ANS 1 ) 3 ENTER 8.666666667

3 ENTER 2.555555556

4 ENTER .5185185185

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n

nn �

n � 13

n � 27.n � 1

3

z � 2.y � �1,x � 1,�

9

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1

�12

�23

�5

305�� x

�x2x

�

�

�

2y3y5y

�

�

3z

5z

�

�

�

9�417

a�1a


Figure IV.95: Iteration

Press ENTER several more times and see what happens with this iteration. You may wish to try it again witha different starting value.

IV.8.2 Terms of Sequences: Another way to display the terms of a sequence is to enter the sequence and thenumber of terms you want listed. For example, to find the first five terms of the sequence press 2nd MATH 3 [List] 1 [seq( ] (-) alpha N + 4 , alpha N , 1 , 5 , 1 ) ENTER (see Figure IV.96). Theformat of this command is seq(expression, variable, low, high, step).

Figure IV.96: Terms of sequence

IV.8.3 Arithmetic and Geometric Sequences: Use iteration with the ANS variable to determine the termof a sequence. For example, find the 18th term of an arithmetic sequence whose first term is 7 and whosecommon difference is 4. Enter the first term 7, then start the progression with the recursion formula, 2nd ANS + 4 ENTER. This yields the 2nd term, so press ENTER sixteen more times to find the 18th term,75. For a geometric sequence whose common ratio is 4, start the progression with 2nd ANS 4 ENTER.

You can also define the sequence recursively with the TI-89 by selecting SEQUENCE in the Graph type onthe first page of the MODE menu (see Figure IV.1). Once again, let’s find the 18th term of an arithmeticsequence whose first term is 7 and whose common difference is 4. Press MODE 4 [SEQUENCE] ENTER.Then press Y= to edit any of the TI-89’s sequences, u1 through u99. Make u1 andui1 7 by pressing alpha U 1 ( alpha N 1 ) + 4 ENTER 7 ENTER (Figure IV.97). Press 2nd QUITto return to the home screen. To find the 18th term of this sequence, calculate u1(18) by pressing alpha U 1 ( 18 ) ENTER (see Figure IV.98).

Figure IV.97: Sequence Y= menu Figure IV.98: Sequence mode

��u1�n � 1� � 4�

�

nth

un � �n � 4

un � �n � 4,


Of course, you could also use the explicit formula for the term of an arithmetic sequence,First enter values for the variables a, d, and n, then evaluate the formula by pressing

alpha A + ( alpha N 1 ) alpha D ENTER. For a geometric sequence whose term is given byenter values for the variables a, n, and r, then evaluate the formula by pressing alpha A alpha

R ^ ( alpha N 1 ) ENTER.

To use the explicit formula in sequence mode, make u1 by pressing Y= then usingto move up to the u1 line and pressing CLEAR 7 + ( N 1 ) 4 ENTER 2nd QUIT. Once more,

calculate u1(18) by pressing alpha U 1 ( 18 ) ENTER.

IV.8.4 Finding Sums and Partial Sums of Sequences: You can find the sum of a sequence by combiningthe sum( feature with the seq( feature on the List sub-menu of the MATH menu. The format of the sum(command is sum(list). The format of the seq( command is seq(expression, variable, low, high, step) wherethe step argument is optional and the default is for integer values from low to high.

For example, suppose you want to find the sum Press 2nd MATH 3 6 [sum(] 2nd MATH 3 1 4

( . 3 ) ^ alpha N , alpha N , 1 , 12 ) ) ENTER (Figure IV.99). The seq( command generates a list, whichthe sum( command then sums. Note that any letter can be used for the variable in the sum, i.e., the N couldjust have easily been an A or a K.

Figure IV.99:

Now calculate the sum starting at by using , , and to edit the range. You should obtain a sumof approximately 1.71284803.

The seq( feature can also be combined with the cumSum( feature to find partial sums of a series. The format of the cumSum( command is cumSum(list).

For example, suppose you want to find the first four partial sums of the series Press 2nd MATH

3 7 [cumSum(] 2nd MATH 3 1 3 ^ ( alpha N + 1) , alpha N , 1 , 4 ) ) ENTER (Figure IV.101).

Figure IV.100: Partial sums of �4

n�13n�1

�4

n�13n�1.

n � 0

�12

n�14�0.3�n

�12

n�14�0.3�n.

�� 7 � �n � 1� � 4

�tn � a � rn�1,

nth�tn � a � �n � 1�d.

nth


IV.8.5 Limit of a Sequence: You can find the limit of a sequence using the limit( command in the CALC

menu. For example, to find press F3 to access the CALC menu and select 3. The

calculator displays limit( and waits for you to enter the expression, variable, point, and direction (if desired).The point is the value being approached by the variable. The direction applies when evaluating one-sidedlimits, and can be omitted here. For this example, press 2 alpha N ^ 2 / ( 5 alpha N ^ 2 – 10 alpha N +3 ) , alpha N , ) ENTER. The calculator returns a value of as shown in Figure IV.101.

Figure IV.101: Limit of a sequence

IV.8.6 Evaluating Infinite Sums: The command allows you to evaluate an infinite sum. For example,

to evaluate press F3 to access the CALC menu and select 4. The calculator displays and

waits for you to enter the expression, variable, and lower and upper limits of summation. For this example,press 2 ( 7 / 6 ) ^ alpha N , alpha N , 0 , ) ENTER. The calculator returns a value of as shownin Figure IV.102.

Figure IV.102: Value of infinite sum

IV.8.7 Taylor Polynomials: The TI-89 allows you to find Taylor polynomial approximations of functions.You can access the taylor( command in the CALC menu by pressing F3 9. The calculator then displays taylor( and waits for you to enter the expression, variable, order, and point (if desired). The point is the center of the power series; if you leave it blank, the default value is zero.

For example, to find the fourth-degree Taylor polynomial for press F3 9 1 / ( 2 + 3 X ̂2 ) ,

X , 4 ) ENTER. The calculator gives a Taylor approximation of as shown in Figure

IV.103. You can compare the graphs of the Taylor polynomial and the actual function by entering both functions into the Y= menu and graphing them in the same window (see Figure IV.104).

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8�

3x2

4�

12

,

f�x� �1

2 � 3x2,

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,

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Figure IV.103: Taylor polynomial Figure IV.104: Comparing graphs

Technology Tip: When graphing the Taylor polynomial, you can avoid entering the expression by hand inthe Y= menu by first copying it to the clipboard. After you have executed the taylor( function, press untilthe expression is highlighted in the history area and press COPY. Then, in the Y= menu, place the cursor in an empty function, press PASTE ENTER, and the polynomial is inserted there.

IV.9 Parametric and Polar Graphs

IV.9.1 Graphing Parametric Equations: The TI-89 plots up to 99 pairs of parametric equations as easily asit plots functions. In the first page of the MODE menu (Figure IV.1) change the Graph setting toPARAMETRIC. Be sure, if the independent parameter is an angle measure, that the angle measure in theMODE menu is set to whichever you need, RADIAN or DEGREE.

For example, here are the keystrokes needed to graph the parametric equations and First check that angles are currently being measured in radians and change to parametric mode. Then press

Y= ( 2nd COS T ) ) ^ 3 ENTER ( 2nd SIN T ) ) ^ 3 ENTER (Figure IV.105).

Figure IV.105: Parametric Y= menu Figure IV.106: Parametric WINDOW menu

Press WINDOW to set the graphing window and to initialize the values of . In the standard window, the

values of go from 0 to in steps of with the view from 10 to 10 in both directions. In

order to provide a better viewing window, press ENTER three times to move the cursor down, and set thewindow to extend from to 2 in both directions (Figure IV.106). Press GRAPH to see the parametricgraph (Figure IV.107).

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24� 0.1309,2�t

t

y � sin3 t.x � cos3 t


Figure IV.107: Parametric graph of and

You may zoom and trace along parametric graphs just as you did with function graphs. However, unlike with function graphs, the cursor will not move to values outside of the t range, so will not work when tand will not work when t As you trace along this graph, notice that the cursor moves in thecounterclockwise direction as t increases.

IV.9.2 Rectangular-Polar Coordinate Conversion: The Angle sub-menu of the MATH menu provides afunction for converting between rectangular and polar coordinate systems. These functions use the currentangle measure setting, so it is a good idea to check the default angle measure before any conversion. Ofcourse, you may override the current angle measure setting, as explained in Section IV.4.1. For the followingexamples, the TI-89 is set to radian mode.

Given the rectangular coordinates, convert from these rectangular coordinates to polarcoordinates by pressing 2nd MATH 2 5 [R�Pr( ] 4 , (-) 3 ) ENTER to display the value of Nowpress 2nd MATH 2 6 [R�P (] 4 , (-) 3 ) ENTER to display the value of (see Figure IV.108).

Figure IV.108: Rectangular to polar coordinates Figure IV.109: Polar to rectangular coordinates

Suppose To convert from these polar coordinates to rectangular coordinates press 2ndMATH 2 3 [P�Rx(] 3 , 2nd ) ENTER to display the coordinate. Now press 2nd MATH 2 4 [P�Ry(]3 , 2nd ) ENTER to display the coordinate (see Figure IV.109).

IV.9.3 Graphing Polar Equations: The TI-89 graphs polar functions in the form In the Graph lineof the first page of the MODE menu, select POLAR for polar graphs. You may now graph up to 99 polarfunctions at one time. Be sure that the angle measure has been set to whichever you need, RADIAN orDEGREE. Here we will use radian measure.

For example, to graph press Y= for the polar graph editing screen. Then enter the expression4 sin for r1 by pressing 4 2nd SIN ) ENTER (see Figure IV.110). The function is located to theright of the ^ key. Choose a good viewing window and an appropriate interval and increment for InFigure IV.111, the viewing window is roughly “square” and extends from to 12 horizontally and from

to 6 vertically.�6�12

.

sin ,r � 4

r � f � �.

y-�x-�

�x, y�,�r, � � �3, ��.

r.�r, �

�x, y� � �4, �3�,

� 2�.

� 0,

y � sin3 tx � cos3 t

2

−2

−2 2


Figure IV.111 shows rectangular coordinates of the cursor’s location on the graph. You may sometimes wishto trace along the curve and see polar coordinates of the cursor’s location. The first line of the GraphFormat menu (Figure IV.25) has options for displaying the cursor’s position in rectangular (RECT) or polar(POLAR) form.

Figure IV.110: Polar Y= menu Figure IV.111: Polar graph of sin

IV.10 Probability and Statistics

IV.10.1 Random Numbers: The command rand( generates numbers. You will find this command in theProbability sub-menu of the MATH menu. Press 2nd MATH 7 4 [rand( ] ) ENTER to generate a randomnumber between 0 and 1. Press ENTER to generate another number; keep pressing ENTER to generatemore of them.

If you need a random number between, say, 0 and 10, then press 10 2nd MATH 7 4 ) ENTER. To get arandom number between 5 and 15, press 5 + 10 2nd MATH 7 4 ) ENTER.

If you need the random number to be an integer between 1 and 10 (inclusive), press 2nd MATH 7 4 10 )ENTER. For a random negative integer between and (inclusive), press 2nd MATH 7 4 (-)10 ) ENTER.

IV.10.2 Permutations and Combinations: To calculate the number of permutations of 12 objects taken 7 ata time, press 2nd MATH 7 2 [nPr( ] 12 , 7 ) ENTER. So, as shown in Figure IV.112.

Figure IV.112: and

For the number of combinations of 12 objects taken 7 at a time, press 2nd MATH 7 3 [nCr( ] 12 , 7 )ENTER. So, as shown in Figure IV.112.

IV.10.3 Probability of Winning: A state lottery is configured so that each player chooses six differentnumbers from 1 to 40. If these six numbers match the six numbers drawn by the State Lottery Commission,the player wins the top prize. There are ways for the six numbers to be drawn. If you purchase a singlelottery ticket, your probability of winning is 1 in Press 1 2nd MATH 7 3 40 , 6 ) ENTER tocalculate your chances, but don’t be disappointed.

�40C6.40C6

12C7 � 792,12C7,

12C712P7

12 P7 � 3,991,680,12P7,

�10�1

r � 4

6

−6

−12 12


IV.10.4 Sum of Data: The following data are a student’s scores on 8 quizzes and 2 tests throughout analgebra course.

25, 20, 18, 89, 17, 24, 23, 22, 25, 93

To find the total points earned by the student, first enter the data using the TI-89’s list editor. Press APPS 6 3 3 [List] S C O R E S ENTER ENTER to open a new variable called SCORES (see FigureIV.113). Now begin entering the test scores as shown in Figure IV.114. Then press 2nd QUIT. To find thesum of the scores, press 2nd MATH 3 6 2nd a-lock S C O R E S alpha ) ENTER. From Figure IV.115,the student earned 356 points throughout the algebra course.

Figure IV.113: Entering a new variable Figure IV.114: List editor

Figure IV.115: Sum

IV.10.5 Statistics: The following data are the high temperatures (in degrees Fahrenheit) recorded in Lincoln,Nebraska from September 3, 2006 to September 14, 2006. (Source: Weather Underground)

78, 75, 82, 84, 85, 84, 69, 70, 64, 74, 82, 85

To find the mean and median of these temperatures, first enter the data using the TI-89’s list editor. PressAPPS 6 3 3 T E M P S ENTER ENTER to open a new variable called TEMPS (see FigureIV.116). Now begin entering the temperatures as shown in Figure IV.117. Then press 2nd QUIT. To find themean, press 2nd MATH 6 [Statistics] 4 [mean( ] 2nd a-lock T E M P S alpha ) ENTER and to find themedian, press 2nd MATH 6 7 [median( ] 2nd a-lock T E M P S alpha ) ENTER (see Figure IV.118). So,the mean of the temperatures is approximately and the median is

Figure IV.116: Entering a new variable Figure IV.117: List editor

80�F.78�F


Figure IV.118: Mean and median

You can also find the mean and median of the above data by using the OneVar command found in the Calcmenu of the Data/Matrix Editor. You can copy the data you entered in Figure IV.112 to a data list by openingthe TEMPS list first. Then press F1 2 [Save Copy As…] 1 [Data] T E M P S alpha 2 ENTERENTER (see Figure V.119). Note that you cannot name the data list TEMPS. Now, to use the OneVarcommand you must have the data list TEMPS2 open. Then press F5 [Calc]. For the Calculation Type,choose 1 [OneVar], set the variable to c1, and press ENTER ENTER. The TI-89 will calculate severaldifferent statistical values. The first line represents the mean of the data which is approximately 78 F (seeFigure IV.120). The second line is the sum of the data, the third line is the sum of the squares of the data, thefourth line is the sample standard deviation of the data, the fifth line is the number of data values, the sixthline is the minimum value of the data, the seventh line is the first quartile of the data, and the eighth line isthe median of the data which is 80 F (see Figure IV.121). The ninth line is the third quartile of the data andthe tenth line is the maximum value of the data.

Figure IV.119: Saving a list as a data list Figure IV.120: OneVar command

Figure IV.121: OneVar command

You can scroll through the list of statistical values by pressing or .

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�x


IV.10.6 Evaluating Normal Probability Density Functions: When a data set is normally distributed, youcan use the TI-89 to compute the probability of selecting an outcome that falls within a given range. Firstyou must use TI Connect to install the Statistics with List Editor Flash application for the TI-89 on your calculator. This application is available for download at www.ti.com/calc. Once you have downloaded andinstalled the application, it can be used to solve the problem below.

Suppose the Scholastic Aptitude Test (SAT) math scores for a given year are normally distributed with amean of 514 and a standard deviation of 113. If you select a person who took the SAT during the given year,the probability that the person scored between 700 and 800 on the math portion is

To compute this probability, press APPS and highlight the Stats/List Editor in the list of Flash applications.Pressing ENTER first takes you to the list editor, because this application allows you to analyze statisticaldata in lists. You can ignore the list editor because it is not needed for this example. Press F5 to access theDISTR menu and press 4 for the Normal Cdf command. As shown in Figure IV.122, the calculator displaysthe problem-entry dialog box for the Normal Cdf function and waits for you to enter the lower bound, upperbound, mean (if desired), and standard deviation (if desired). If you do not change the mean and standard deviation, the calculator uses the default values of and that are displayed. In this case,these default values are not appropriate, so you will need to change them. Enter 700 for the lower bound,800 for the upper bound, 514 for the mean, and 113 for the standard deviation. Then press ENTER, and thecalculator displays a summary window with the probability given as Cdf = .044193, as shown in FigureIV.123.

Figure IV.122: Normal Cdf dialog box Figure IV.123: Normal Cdf summary

The computation shows that the probability of selecting a person who scored between 700 and 800 is about0.044, or 4.4%.

IV.11 Derivatives

IV.11.1 Differentiation: You can differentiate a function symbolically using the d( command. Press F3 toaccess the CALC menu and select 1 (or, instead of going through the CALC menu you can simply press 2nd d ). The calculator displays d( and waits for you to enter the expression, variable, and order (if desired).If you do not specify an order, the calculator computes a first derivative. If you do specify an order, it mustbe an integer (a negative order results in an anti-derivative). Press X ^ 2 + X / 3 – 2 , X ) ENTER to findthe first derivative of the function The result is shown in Figure IV.124. f �x� � x2 �

13 x � 2.

� � 1� � 0��

P�700 ≤ x ≤ 800� � �800

700

1

113�2p e��x� 514�2�2�113�2

dx.


Figure IV.124: Differentiate symbolically

IV.11.2 Numerical Derivatives: There are two different approaches when using the TI-89 to approximatenumerical derivatives; one method involves graphing, and one does not. Each method is described below tofind the numerical derivative of at

Non-Graphing Method: Press F3 to access the CALC menu. Here, there are two different commands youcan use to compute the numerical derivative at a specific value: d( and nDeriv(.

To use d(, select 1 from the CALC menu or just press 2nd d(. The calculator then displays d( and waits foryou to enter the expression, variable, and order (if desired). If you do not specify an order, the calculatorcomputes a first derivative. Press X ^ 2 + X / 3 – 2 , X ). However, before pressing enter, press X = 2 toevaluate this derivative when Now press ENTER. The result is shown in Figure IV.125.

Figure IV.125: Using d( command Figure IV.126: Using nDeriv( command

To use nDeriv(, select A from the CALC menu. The calculator then displays nDeriv( and waits for you to enter the expression, variable, and the step value h (if desired). If you do not specify a value of h, the calculator uses a default value of 0.001. Press X ^ 2 + X / 3 – 2 , X ). However, before pressing enter, press

X = 2 to evaluate this derivative when Now press ENTER. The result is shown in Figure IV.126.

Both of these commands give similar results, but nDeriv( may not be as exact because it finds the slope ofthe secant line through the points and and therefore depends upon thevalue of The command d( differentiates exactly and is more accurate than nDeriv(.

Graphing Method: First press Y=, enter the expression into the Y= menu, and graph thefunction. It does not matter what viewing window you choose, as long as it contains the x-value at which youwill be evaluating the derivative. From the graph screen, press F5 6 to access the Derivatives menu, andthen press 1 to select dy/dx from the submenu, as shown in Figure IV.127. The calculator then displays thegraph and waits for you to choose an x-value. (If more than one function is graphed, you must first select thefunction you want, using the up and down cursor keys.) To choose an x-value, either move the cursor to thepoint using the left and right cursor keys, or type a specific value. (The x-coordinate and y-coordinate arelabeled as xc and yc, respectively.) After selecting an x-value, press ENTER, and the calculator displays thenumerical derivative at that x-value, as shown in Figure IV.128.

x2 �13 x � 2

h.�x � h, f�x � h��,�x � h, f�x � h��

x � 2.

x � 2.

x � 2. f�x� � x2 �13 x � 2


Figure IV.127: Derivatives menu Figure IV.128: Numerical derivative

Technology Tip: To continue finding additional numerical derivatives at different x-values of the same function, simply press the left or right cursor key to restore the free-moving cursor on the screen, then repeatthe process given above.

IV.12 Integration

IV.12.1 Indefinite Integrals: You can integrate a function symbolically using the ( command. To findpress F3 to access the CALC menu and select 2. Or, instead of going through the CALC menu

you can simply press 2nd The calculator displays ( and waits for you to enter the expression, variable,and limits or a constant of integration (if desired). If you specify a constant of integration such as C, the calculator displays the anti-derivative with the constant of integration. For this example, press 3 X ^ 3 – 1 ,X , ALPHA C ) ENTER. The result, is shown in Figure IV.129.

Figure IV.129: Integrate symbolically

IV.12.2 Definite Integrals: There are two different approaches when using the TI-89 to evaluate definiteintegrals; one method involves graphing, and one does not. Each method is described below to evaluate thedefinite integral

Non-Graphing Method: Press F3 to access the CALC menu and select 2. Or, instead of going through the CALC menu you can simply press 2nd The calculator displays ( and waits for you to enter theexpression, variable, and limits or a constant of integration (if desired). In this case you will enter lower andupper limits of integration so that the calculator can evaluate the definite integral. For this example, press X ^ 2 / 2 + 2 , X , 0 , 2 ) ENTER. The result is shown in Figure IV.130.

Figure IV.130: Evaluating a definite integral

��.

�20 �1

2x2 � 2�dx.

34x4 � x � C,

��.��3x3 � 1�dx,

�


Graphing Method: First press Y=, enter the expression into the Y= menu, and graph the function. Make sure that your viewing window contains the x-values of the lower and upper limits of integration. From the graph screen, press F5 7 to access the f(x)dx feature, as seen in Figure IV.131. Thecalculator now waits for you to choose the lower and upper limits of integration. (If more than one functionis graphed, you must first select the function you want, using the up and down cursor keys.) The displayprompts you for the lower limit of integration by displaying “Lower Limit?” on the screen (see FigureIV.132). To choose the lower limit, either move the cursor to the point using the left and right cursor keys,or type a specific value. (The x-coordinate and y-coordinate are labeled as xc and yc, respectively.) Afterselecting a lower limit, press ENTER, and the calculator then displays “Upper Limit?” on the screen (seeFigure IV.133). After you select an upper limit and press ENTER, the calculator shades the region whosearea is being calculated, and displays an approximation of the definite integral, as shown in Figure IV.134.

Figure IV.131: GRAPH MATH menu Figure IV.132: Setting lower limit

Figure IV.133: Setting upper limit Figure IV.134: Definite integral

Technology Tip: Because the shaded area is considered a drawing, you can clear it from the graph by pressing F4. (You can also access this ClrDraw command by pressing 2nd F6 1.) The calculator redrawsthe current graph without the shaded area.

IV.12.3 Improper Integrals: To evaluate improper integrals on the TI-89, you use the non-graphing technique for evaluating definite integrals described above. Press F3 to access the CALC menu and select 2.Or, instead of going through the CALC menu you can simply press 2nd . The calculator displays ( andwaits for you to enter the expression, variable, and in this case the lower and upper limits of integration.

If the integrand does not have an infinite discontinuity somewhere in the interval of integration, you can simply enter the limits into the appropriate place in the ( command and the calculator will compute the

limit. For example, to evaluate place ( in the entry line and press 1 / X , X , 1 , ) ENTER. The

limit is (see Figure IV.135), so the infinite integral diverges�

��

1

1x dx,

�

��

�

12 x2 � 2


Figure IV.135: Evaluating an improper integral

If the integrand has an infinite discontinuity somewhere in the interval of integration, the calculator mayreturn a value of undef. Integrals like these should first be rewritten as the sum of two integrals; then you canuse the TI-89 to evaluate each of those integrals and analyze the results. For example, when the calculator

evaluates it displays undef (see Figure IV.136).

Figure IV.136: Infinite discontinuity

Recognizing that the integrand has an infinite discontinuity at you can write

and evaluate and The result (see Figure IV.137) shows that each of these

integrals diverges, so you can conclude that the original integral diverges

Figure IV.137: Evaluating rewritten integrals

�0

�1

1�x � 1�5 dx.��1

�2

1�x � 1�5 dx

�0

�2

1�x � 1�5 dx � ��1

�2

1�x � 1� dx � �0

�1

1�x � 1�5 dx

x � �1,

�0

�2

1�x � 1�5 dx,


IV.13 Three-Dimensional Graphing

IV.13.1 Entering 3D Equations: Before entering and graphing three-dimensional equations, you mustchange the graph mode to 3D by pressing MODE 5 ENTER. Now when you press Y= to open thefunction editing screen, the functions are named z instead of y. Move the cursor to z1 and press CLEAR todelete the contents, if needed. Then define the 3D equation. (In this context, implied multiplication betweenvariables is allowed.) To enter the function press Y ^ 2 / 4 – X ^ 2 ENTER (see FigureIV.138). Make sure that z1 is selected with a checkmark; if not, press F4 to select the function. In 3D graph-ing mode, you can select only one equation at a time.

Figure IV.138: Entering a 3D equation

IV.13.2 Setting the Viewing Cube: Once you have entered the equation, press WINDOW (FiguresIV.139 and IV.140) to define the viewing cube. The viewing window is called a viewing cube for 3D graphs,because the graphs are displayed in three-dimensions.

Figure IV.139: Window variables Figure IV.140: More window variables

Viewing Angle: The variables and are angle settings that determine the vantage point from which you view the graph. To rotate the viewing angle around the z-axis, change To change the elevation of the viewing angle above or below the xy-plane, change ; values of 90 < < 270 viewthe graph from below the xy-plane. Once your viewing angle is set, the variable determines the angleby which the graph is rotated around that line of sight. It is common to keep the default value of =0,because this shows the z-axis as vertical. Increasing this angle would be like standing still in one spot androtating your head around counterclockwise.

Axis Settings: The boundaries of the viewing cube are set by the values of xmin, xmax, ymin, ymax, zmin,and zmax. The values of xgrid and ygrid determine the number of grids that the x-axis and y-axis are divided into. The equation is evaluated at every point where the grids intersect, and in wireframe viewthe calculator plots points at these coordinates and connects them with line segments, giving the surface itswireframe appearance.

�x, y�

eye�eye�

eye�eye�eye .

eye�eye�,eye ,

f�x, y� �14 y2 � x2,


Contour Setting: The variable ncontour defines the number of divisions of the z-axis when using one of thecontour styles in the GRAPH FORMATS screen. The total distance between zmin and zmax is divided bythe value of ncontour and this is the increment used when drawing contours on the surface. For example, if

and the increment is equal to so the contours will be 4 unitsapart. Contours are traces along the surface at specific values of z. The value of ncontour will not affect anything if you choose not to include contours on your graph.

IV.13.3 Setting the Graph Format: You can access the GRAPH FORMATS screen by pressing F1 9.When graphing 3D equations, it is helpful to have the axes setting turned on; to do this you may select AXES(showing the x-, y-, and z-axes) or BOX (showing a box around the edge of the viewing cube). In either case,make sure that the labels are set to ON, so that you can get your bearings when viewing the graph.

The style setting determines how the surface is drawn. WIRE FRAME draws the surface as a wireframe withno shading; HIDDEN SURFACES is similar to wire frame but uses shading to hide parts of the surface thatare hidden from your viewpoint. The CONTOUR LEVELS style does not draw a wire frame, but insteadshows the contours, or traces, along the surface at specific values of z determined by ncontour in the window settings. The style WIRE AND CONTOUR combines the wire frame and contour views. TheIMPLICIT PLOT style is useful when you have the implicit form of an equation. For implicit plots, only the

contour is drawn, showing where the surface intersects the xy-plane. All five of these style formats areillustrated in Figures IV.141 - IV.145 for the function

Figure IV.141: Wire frame Figure IV.142: Hidden surfaces

Figure IV.143: Contour levels Figure IV.144: Wire and contour

Figure IV.145: Implicit plot

f�x, y� �14 y2 � x2.

z � 0

205 � 4,ncontour � 5,zmax � 10,zmin � �10,


Technology Tip: When you choose either CONTOUR LEVELS or IMPLICIT PLOT, the calculator initially sets the viewing angles so you are looking straight down the z-axis onto the xy-plane, and the labelsare set to OFF. You can change these settings as desired. Also, the graph is initially shown in expanded view.You can switch between expanded view and normal view by pressing ✕.

IV.13.4 Graphing and Exploring the Graph: Press GRAPH to view the graph. While processing the equation, the calculator shows its evaluation progress in percentages on the screen. Once the graph appears,you can explore the graph by zooming, tracing, evaluating, changing views, and animating the graph.

Zooming: Press F2 to access the zoom features. They work the same here as they do for 2D graphs, but onlycertain zoom features are available; the others are ghosted. When you zoom, keep in mind that your grid andeye window variables are not affected unless you use the ZoomStd command, which resets all window variables to the default values.

Tracing: Tracing 3D graphs is very similar to tracing 2D graphs. However, it is important to understand howthe cursor moves when you press the cursor arrows. The cursor always moves from one grid point to the nextalong one of the line segments of the wire frame. So, it only moves in the x-direction or the y-direction atone time; it does not move diagonally across the grid. Pressing or moves in a negative or positive x-direction, and pressing or moves in a negative or positive y-direction. To try this with an example,graph the equation using the window settings given in section IV.13.2 and using the HIDDEN SURFACES style. Now press F3 to access the trace feature. The cursor begins at the midpointof the xy grid, in this case the origin, as shown in Figure IV.146. Now press to move the cursor one gridunit in the positive x-direction. Notice that the x-coordinate increases, the y-coordinate stays the same, andthe z-coordinate decreases (see Figure IV.147). This is because you are moving along the surface in the direction of the positive x-axis, and the surface curves downward, causing the z-values to decrease. Continuepressing and you will see this continues, as shown in Figures IV.148 and IV.149. Now try pressing the upand down cursor keys to see that the y-coordinate increments but the x-coordinate stays constant.

Figure IV.146: Trace at Figure IV.147: Pressing

Figure IV.148: Pressing again Figure IV.149: Pressing again

�0, 0, 0�

f�x, y� �14 y2 � x2


Technology Tip: Sometimes the cursor may not always appear to be on a grid point, if you are tracing alonga hidden portion of the surface. Or, sometimes the cursor can actually appear to be floating off of the surface. This happens when the boundaries of the z-axis are cropping part of the surface; the trace cursor continues to move along within the xy grid but is unable to display the cursor on the surface itself becausethe z-coordinate is not visible in the viewing cube. The calculator does, however, display the correct z-coordinate on the screen. This is why it is extremely helpful to have axis labels ON when tracing and payattention to the trace coordinates displayed on the screen.

Evaluating: From the graph screen you can evaluate a function at a specific point by pressing F5[MATH] and selecting value. For example, to evaluate the function above at and press F5 1 2ENTER 3 ENTER . The calculator shows a cursor at the point on the surface and displays the z-coordinateas as shown in Figure IV.150.

Figure IV.150: Evaluating a function

You can also evaluate during a trace by simply typing the x-value and pressing ENTER, then typing the y-value and pressing ENTER.

Changing Views: Pressing the cursor keys left, right, up, or down rotates the graph in that direction. Tryrepeatedly pressing one cursor key to see the graph rotating incrementally. You can also press X, Y, and Z toplace your viewpoint at the positive end of that axis. For example, begin with the graph described and shownabove in Figure IV.142. Now when you press X, Y, and Z, you get the views shown below. No matter howyou have altered your viewpoint, pressing 0 always returns you back to the original graph as specified inyour window settings.

Figure IV.151: Pressing X Figure IV.152: Pressing Y

Figure IV.153: Pressing Z Figure IV.154: Pressing 0

�1.75,

y � 3,x � 2�x, y�


Animating: When you pressed the cursor keys above to change views in increments, you were actually animating the graph, but one step at a time. You can have the graph animate on its own by pressing and holding one of the cursor keys for about 1 second, then releasing it. The graph then rotates in that directioncontinuously until you stop the animation by pressing ESC, ENTER, ON, or alpha . During the anima-tion, if you want to increase or decrease the speed, press + or – (this increases or decreases the angle incre-ment between viewpoints). Remember, after an animation you can restore the graph to its original viewpointby pressing 0.

Technology Tip: There are countless other tips and shortcut keys for changing settings while you are viewing a three-dimensional graph; you can consult your TI-89 manual for a thorough review of these tips.For example, on the 3D graph screen you can press alpha F to switch from one format style to the next.

IV.14 Partial Derivatives

IV.14.1 First-Order Partial Derivatives: The d( command that you use for differentiation can also be usedto find partial derivatives. You specify the variable, and the calculator computes the partial derivative withrespect to that variable. This feature works for functions of two, three, or more variables. The example belowshows how to compute the first partial derivatives of

To differentiate with respect to x, press 2nd d 4 X ^ 2 + 3 X * Y – Y ^ 2 , X ) ENTER. You get the resultshown in Figure IV.155. After computing the partial derivative with respect to while the command is stillhighlighted in the entry line, press once to get the cursor at the end of the line, then press Y to replace

with in the command line, then press ENTER to find the partial derivative with respect to (see FigureIV.156).

Figure IV.155: Finding Figure IV.156: Finding

So, the first partial derivatives are and

Technology Tip: Because the TI-89 requires multiplication to be expressed between variables, if a term con-tains a product involving two or more variables, you must use the ✕ key instead of implied multiplication.In the example above, the second term of the expression was entered as 3x * y, not 3xy.

IV.14.2 Higher-Order Partial Derivatives: To compute higher-order partial derivatives, you can specify theorder within the d( command or, for mixed partial derivatives, you can use one d( command nested withinanother. The example below illustrates these techniques for finding the second partial derivatives of

You want to differentiate twice with respect to so you can simply enter as the variable and 2 asthe order, and the calculator will compute the second partial derivative. Press 2nd d X ^ 2 * Y – 3 X + X ^2 * Y ^ 2 , X , 2 ) ENTER. The result is shown in Figure IV.157.

You want to differentiate twice with respect to so you can simply enter as the variable and 2 asthe order, and the calculator will compute the second partial derivative. Press 2nd d X ^ 2 * Y – 3 X + X ^2 * Y ^ 2 , Y , 2 ) ENTER. The result is shown in Figure IV.158.

You want to differentiate first with respect to and then with respect to so you need to use y,x fxy�x, y�:

yy, fyy�x, y�:

xx, fxx�x, y�:

f�x, y� � x2y � x � x2y2.

fy�x, y� � 3x � 2y. fx�x, y� � 8x � 3y

fy�x, y� fx�x, y�

yyx

x,

f �x, y� � 4x2 � 3xy � y2.


[

nested d( commands. Press 2nd d 2nd d X ^ 2 * Y – 3 X + X ^ 2 * Y ^ 2 , X ) , Y ) ENTER, as shown in Figure IV.159. The calculator first differentiates the function with respect to and then the result is differentiated with respect to

You want to differentiate first with respect to and then with respect to so you need to use nested d( commands. Press 2nd d 2nd d X ^ 2 * Y – 3 X + X ^ 2 * Y ^ 2 , Y ) , X ) ENTER, as shown inFigure IV.160. The calculator first differentiates the function with respect to and then the result is differ-entiated with respect to



IV.15 Partial Integration

IV.15.1 Partial Integrals: The ( command that you use for integration can also be used to find partial integrals. You specify the variable, and the calculator computes the partial integral with respect to that variable. For example, to evaluate the partial integral you integrate with respect to Press2nd 4 X * Y – Y , Y , 0 , X ) ENTER, as shown in Figure IV.161.

Figure IV.161: Finding a partial integral

�y.�x

0 �4xy � y�dy,

�

fyx�x, y� fxy�x, y�

fyy�x, y� fxx�x, y�

x.y,

x,y fyx�x, y�:

y.x,


IV.15.2 Double Integrals: To find double integrals, you can use one ( command nested within another. Theexample here shows how to evaluate the double integral For definite integrals, the for-mat of the command is ( expression, variable, lower limit, upper limit ). The first thing you want the cal-culator to do is to evaluate which is achieved by entering (4x*y – y, y, 0, x). But you wantthis command to be nested inside another ( command that will integrate the result with respect to Thecomplete nested command will look like this:

( (4x*y – y, y, 0, x), x, 1, 2)

The keystrokes are 2nd 2nd 4 X * Y – Y , Y , 0 , X ) , X , 1 , 2 ), and the result is shown in FigureIV.162.

Figure IV.162: Evaluating a double integral

IV.16 Differential Equations

IV.16.1 General Solutions: You can find the general solution of a separable variables differential equationon the TI-89 using deSolve(. The process is shown below for the differential equation Beforeusing deSolve(, you need to clear any existing values for variables and in the calculator’s memory. Press2nd F6 1, then press ENTER to confirm this action.

Now press F3 [Calc] ENTER to obtain the deSolve( command. The calculator displays deSolve( in theentry line and waits for you to enter the equation, the independent variable, and the dependent variable. Forthe equation given above, press Y 2nd = X ^ 2 – 5, X , Y ) ENTER, as shown in Figure IV.163.

Figure IV.163: Finidng a general solution

When the TI-89 displays constants in general solutions, they are shown as @ where is an integer from 1 through 255. In the figure shown here, @1 represents the constant, but this is arbitrary; the constant couldhave been named @2, @3, @4, or any other version of @ Using to represent the constant, you could

rewrite this general solution as

Technology Tip: When entering differential equations, if you have a variable multiplied by a parentheticalquantity, do not use implied multiplication, or it will be treated as a function call. Instead, use the ✕ key. Forexample, to enter the equation enter y =y*(1+x), not y =y(1+x).��y� � y�1 � x�,

y �x3

3� 5x � C.

Ck.

kk,

�

yxy� � x2 � 5.

��

��

x.��x

0 �4xy � y�dy,�

�21 �x

0 �4xy � y�dy dx.�


IV.16.2 Particular Solutions: Suppose you want to solve the differential equation subject to theinitial condition when You can use deSolve( to find the particular solution directly. Insteadof just entering the equation as the first argument in this command, you enter the equation and the initial condition, separated by the Boolean operator and. To do this, press F3 [Calc] Y 2nd = X ^ 2 – 5 2nd MATH 8 8 Y ( 3 ) = (-) 4 , X , Y ) ENTER. The calculator then displays the particular solution

as shown in Figure IV.164.

Figure IV.164: Fining a particular solution

There is another way to find a particular solution on the TI-89; it is a three-part process, just like the processused when doing the work by hand: (1) find the general solution, (2) compute the constant for a set of initial conditions, and (3) evaluate the general solution using that constant.

Start by using the process described in Part IV.16.1 to obtain the general solution shown in Figure IV.165.Now press to highlight the solution in the history area, press ENTER to paste it into the entry line, thenplace the cursor at the beginning of the entry line and press F4 1 to insert the Define command in front ofthe function. Now press ENTER. The result is shown in Figure IV.166.

Figure IV.165: General solution Figure IV.166: Defining the function

Figure IV.167: Finding the constant Figure IV.168: Particular solution

y �x3

3� 5x � 2,

�

x � 3.y � �4y� � x2 � 5


Now use solve( to find the @1 constant for the initial condition when Press F2 1 Y = (-) 4 ,STO> 1 ) X = 3 ENTER. The result, in Figure IV.167, shows you that the constant @ Finally,

press Y | STO> 1 = 2 ENTER to evaluate the general solution (which you defined as ) when the

constant @ The calculator displays the particular solution as shown in Figure

IV.168.

IV.17 Programming

IV.17.1 Entering a Program: The TI-89 is a programmable calculator that can store sequences ofcommands for later replay. Press APPS 7 [Program Editor] to access the programming menu. The TI-89has space for many programs, each called by a title you give it. To create a new program, start by pressingAPPS 7 3 [New…]. Set the Type to Program and the Folder to main (unless you have another folder inwhich you want to store the program). Enter a descriptive title for the program in the Variable line. Afteryou name the program, press ENTER ENTER to go to the program editor. The program name and thebeginning and ending commands of the program are automatically displayed with the cursor on the first lineafter Prgm, the begin program command.

In the program, each line begins with a colon : supplied automatically by the calculator. Any command youcould enter directly in the TI-89’s home screen can be entered as a line in a program. There are also specialprogramming commands.

You may interrupt programming input at any stage by pressing 2nd QUIT. To return later for more editing,press APPS 7 2 [Open…], move the cursor down to the Variable list, highlight the program’s name, andpress ENTER ENTER.

You may remove a program from memory by pressing 2nd VAR-LINK, move the cursor to highlight thename of the program you want to delete, then press F1 [Manage] 1 [Delete] ENTER.

Technology Tip: If your program uses one-letter variables such as, a, b, c, or d, note that any previousvalues for these variables, including matrices, will be replaced by the values used by the program. The TI-89 does not distinguish between A and a in these uses. Note that you will have to clear the variables(using 2nd VAR-LINK) in order to use these names again in the current folder. From the home screen, press F4 [Other] alpha B [NewFold] and type the name of the new folder. The work you do from that point onwill be in the new folder, as indicated by the folder name in the lower left corner of the status line. You canchange folders from the MODE menu or, from the home screen, by typing setFold( foldername), wherefoldername is the existing folder that you wish to be in.

IV.17.2 Executing a Program: To execute a program you entered, go to the home screen and type the nameof the program, including the parentheses and then press ENTER to execute it. If you have forgotten itsname, press 2nd VAR-LINK to list all the variables that exist. The programs will have PRGM after the name.You can execute the program from this screen by highlighting the name and then pressing ENTER. Thescreen will return to the home screen and you will have to enter the closing parenthesis ) and press ENTERto execute the program.

If you need to interrupt a program during execution, press ON.

The instruction manual for your TI-89 gives detailed information about programming. Refer to it to learnmore about programming and how to use other features of your calculator.

y �x3

3� 5x � 2,1 � 2.

y1 � 2.

x � 3.y � �4


part iv: texas instruments ti-89 graphing calculator iv.1 getting started … · 2008-06-27 ·...

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