chapter 2 solution

Step 3:

SOLVING THEPROBLEMS

The first thing we must do to solve thisproblem is find how long Wilfred and John willbe on the ride before Francis and Kieran getoff.


We can do this by subtracting the time ofWilfred and John’s boarding of the ride fromthe time when Francis and Kieran get off.



35Time that Francis and Kieran will get off



35 - 21Time that Francis and Kieran will get off

How long ‘F’ and ‘K’ have been on the ride when ‘W’ and ‘J’ get on



35 - 21 = 14Time that Francis and Kieran will get off

How long ‘F’ and ‘K’ have been on the ride when ‘W’ and ‘J’ get on

This tells us that Francis and Kieran will be getting off the ferris wheel in 14 minutes.

This tells us that Francis and Kieran will be getting off the ferris wheel in 14 minutes.

Therefore we can conclude that Wilfred and John will have been on the ferris wheel for 14 minutes.

Now that we know how long they have been onthe ride, we must find what height Wilfred and John are at when Francis and Kieran get off.


We can do this by solving one of the equationsthat we derived a few minutes ago with t=14substituted into it.


We can do this by solving one of the equationsthat we derived a few minutes ago with t=14substituted into it.

***I will be using both the sine and cosine equation for this part.***

Sine Equation

Sine Equation

H(t)=75sin((2π/35)(t-10.75))+76

The Original Equation:

Sine Equation

H(14)=75sin((2π/35)(14-10.75))+76

Substitute t=14 into the equation.

Sine Equation

H(14)=75sin((2π/35)3.25)+76

Simplify the brackets.

Sine Equation

H(14)=75sin(6.5π/35)+76


Sine Equation

H(14)=75(0.5509)+76

Calculate the sine of the value inside the brackets.[Accurate to 4 decimal places.]

Sine Equation

H(14)=41.3173+76

Simplify the equation.

Sine Equation

H(14)=117.3173


Sine Equation

H=117.3173m

Cosine Equation

Cosine Equation

H(t)=-75cos((2π/35)(t-2.0))+76


Cosine Equation

H(14)=-75cos((2π/35)(14-2.0))+76

Substitute t=14 into the equation.

Cosine Equation

H(14)=-75cos((2π/35)12.0)+76


Cosine Equation

H(14)=-75cos(24.0π/35)+76


Cosine Equation

H(14)=-75(-0.5509)+76

Calculate the cosine of the value inside the brackets.[Accurate to 4 decimal places.]

Cosine Equation

H(14)=41.3173+76


Cosine Equation

H(14)=117.3173


Cosine Equation

H=117.3173m

This means that Wilfred and John were approximately 117 m off the ground when Francis and Kieran got off.

We have just answered the first part of the question.


Now we must use this to answer the secondpart of the question:


Now we must use this to answer the secondpart of the question:

How much longer will it be until they reach the same height again?

Some people might be confused by thisquestion, so lets take a look at it.


This is the graph that we constructed earlier.


The point on the graph is the point that we just found. (t=14)


The height of this point is 117m.


However, there is another point with a heightof 117m.


Therefore there is another time that theywill reach a height of 117m.

So, we are looking to find that second time which has a height of 117.3173m.

We can do this by making the equation equal to 117.3173m and solving it.

So, we are looking to find that second time which has a height of 117.3173m.

We can do this by making the equation equal to 117.3173m and solving it.

***This time I will only use the Sine equation and explain the difference between the two methods afterwards.***

Sine Equation

Sine Equation

H(t)=75sin((2π/35)(t-10.75))+76


Sine Equation

117.3173=75sin((2π/35)(t-10.75))+76

Substitute H(t)=117.3173 into the equation.

Sine Equation

117.3173=75sinØ+76

Let ((2π/35)(t-10.7))=Ø to make it a little easier to work with.

Sine Equation

41.3173=75sinØ


Sine Equation

0.5509=sinØ


Sine Equation

0.5834=Ø

Calculate the arc sine of 0.5509 [to four decimal places].

Sine Equation

Now we have an angle.

The measure of this angle is 0.5834 radians

Another thing we know about this angle is that it’s sine is positive.

WHY IS THIS HELPFUL???

Sine Equation

Well, when the sine of an angle is positive, it must either be in Quadrant 1 or 2.

This particular angle is in Quadrant 1.

HOW DO WE KNOW THIS???

Well, when the sine of an angle is positive, it must either be in Quadrant 1 or 2.

This particular angle is in Quadrant 1.

HOW DO WE KNOW THIS???

Sine Equation

QIQII

QIII QIV

!/2

0!

3!/2

2!

Here we have the Unit Circle.

Sine Equation

QIQII

QIII QIV

!/2

0!

3!/2

2!

The angle that separates Quadrants I and II is π/2.

[or 1.5707...]

Sine Equation

QIQII

QIII QIV

!/2

0!

3!/2

2!

0.5834 is much less than 1.5708 so it lies in Quadrant I.

Sine EquationThis means that to find the other point with the exact same sine value, it’s angle would have to be in Quadrant II.


To find this angle we simply subtract our angle from π (End of Quadrant II).


To find this angle we simply subtract our angle from π (End of Quadrant II).

π - Ø = Ø’

Sine Equation

2.5582=Ø’

Here we have our Quadrant II angle.

Sine Equation

sinØ=sinØ’

Now the two angles we have are related angles. This means their sine values are equivalent.

Sine Equation

Ø=Ø’

And if we take the arc sine of both sides and we see that:

Sine Equation

Ø=2.5582

Now we can continue where we left off.

Since...

Sine Equation

Ø= ((2π/35)(t-10.7))

...AND...

Sine Equation

2.5582= ((2π/35)(t-10.7))

...Then.

Sine Equation

14.25= (t-10.7)

Now just simplify.

Sine Equation

25= t

Now just simplify.

Sine Equation

t=25Cosine Equation

Cosine Equation

The Cosine equation works quite similarly to that of Sine.

Cosine Equation

The Cosine equation works quite similarly to that of Sine.

The equation is a little bit different as we saw earlier but that’s about all that applies to the first part of the procedure.

Cosine Equation

One of the major differences is when you simplify down to cosØ.

Cosine Equation


First of all, this value is negative which means the angle is either in Quadrant II or III.

Cosine Equation


First of all, this value is negative which means the angle is either in Quadrant II or III.

This one is in Quadrant II because it is 2.1542 which is less than π (3.1415), the end of Quadrant II.

Cosine Equation

This means Ø’ is in Quadrant III and we must subtract Ø (angle that passes Q I and into II) from the full circle (2π) so it passes through Q IV and into III.

Cosine Equation

This means Ø’ is in Quadrant III and we must subtract Ø (angle that passes Q I and into II) from the full circle (2π) so it passes through Q IV and into III.

After that, continue as shown in the Sine procedure until you get t=25 as your answer.

From here, we now can finish the problem off.

t=25 minutes

Since it takes 14 minutes to get from thestart to 117.3173 m the first time.

14

Since it takes 14 minutes to get from thestart to 117.3173 m the first time...

...And it takes 25 minutes to get from the startto 117.3173 m the second time...

14 - 25

...Then the time it takes to get from 117.3173 the first time to 117.3173 m the second timemust equal...

14 - 25 = ?

11 minutes

When Francis and Kieran get off “The Wheel”, Wilfred and John will be 117.3173 m from the ground.

It will take them 11 more minutes to get to that exact same height again.

chapter 2 solution

Technology

time of wilfred

equation equal

long wilfred

cosine equation h

height wilfred

cosine equation substitute

francis andkieran

cosine equationsimplify