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7.4 Reciprocal Functions.notebook
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December 21, 2015
7.4 Reciprocal Functions
1) Graph the reciprocal of a given function.
2) Analyze the graph of the reciprocal of a given function.
3) Compare the graph of a function to the graph of the reciprocal of that function.
4) Identify the values of x for which the graph of y=1/f(x) has vertical asymptotes.
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The reciprocal of 2 is ______, the reciprocal of 2/3 is _____, the reciprocal of y = x is y =
Examination of a function and its reciprocal:
y = x y = 1/x
x y
5311/21/100
1/10013
x y
5311/21/100
1/10013
**Which points are invariant between the two functions:
As the xvalues of y = x get bigger, the yvalues get _____________________
As the xvalues of y = x get smaller, the yvalues get _____________________
As the xvalues of y = 1/x get bigger, the yvalues get _____________________
As the xvalues of y = 1/x get smaller, the yvalues get _____________________
**This gives rise to the generalization that as the yvalues of the original increase, the yvalues of the reciprocal decrease, and as the yvalues of the original decrease, the yvalues of the reciprocal increase. Opposite behaviour.
What do we call the xcoordinates that have a yvalue of 0 ____________________________
What happens to the yvalue for the reciprocal (what is wrong with a yvalue of 1/0)? ______________________________
Therefore, at the xintercepts of the original, we have a yvalue in the reciprocal that cannot exist. We draw a vertical dashed line through the xintercept to represent a yvalue that cannot exist for the reciprocal and call it a vertical asymptote.
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Rules for drawing a Reciprocal function:
1) Draw the "original". If the numerator is 1, the original function is the denominator. e.g. if the function is y = 1/(x22) , then my original is x2 2 and that is what I draw.
2) Put a dot at the invariant points (where the yvalue is 1 or 1). Because they are invariant, they will also exist on the reciprocal.
3) Find the xintercepts. Remember, these are a problem for the reciprocal because they have a yvalue of 0 and 1/0 cannot exist. We draw vertical dashed lines through these intercepts. The reciprocal graph may approach the asymptote but may never touch it.
4) As the original increases or decreases, the reciprocal will do the opposite decrease or increase, respectively.
5) Where the original is positive, the reciprocal is positive. Where the original is negative, the reciprocal is negative.
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page 404 405 #3, 59
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Attachments
buffalo example 2.xlsx
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SMART Notebook
Page 1: Dec 18-9:07 AMPage 2: Dec 18-9:10 AMPage 3: Dec 18-9:37 AMPage 4: Jan 13-11:18 AMPage 5: Dec 18-9:46 AMPage 6: Dec 18-9:46 AMPage 7: Dec 18-9:46 AMPage 8: Dec 18-9:49 AMPage 9: Dec 18-9:46 AMPage 10: Dec 18-9:46 AMAttachments Page 1