Derivatives problem 13.mws

1. Inverse functions.

There are several ways to characterize when two functions are inverses to each other. The graphs of two functions will be reflections of each other across the line y = x precisely when they are inverse functions. This activity is intended to explore the relation between the derivative of a function at the point ( a, b ), and the derivative of the inverse function at the point ( b, a ).

Submission:

(a) Plot the functions f(x) = x^2 and g(x) = sqrt(x) on the same axes, over the domain x=0..5 and range y=0..5. In order to get the proper aspect ratio, you should choose the option scaling=CONSTRAINED to the plot command. How do these graphs illustrate that these are inverse functions?

(b) Find the slope of the tangent line to the curve y = f(x) at the points ( a, b )=(1,1), ( sqrt(2), 2 ), ( sqrt(3), 3 ), ( sqrt(4), 4 ).  Then find the slope of the tangent line to the curve y = g(x) at the points ( b, a )=(1,1), ( 2, sqrt(2) ), ( 3, sqrt(3) ), ( 4, sqrt(4) ).  What is the relation between the slopes of these tangent lines?

(c) Plot the tangent line to the curve y = f(x) at ( sqrt(2), 2 ) and the tangent line to the curve y = g(x) at ( 2, sqrt(2) ) on the same axes, again using a CONSTRAINED scaling. What is the relationship between these two tangent lines?

Submission worksheet: