University Calculus: Early Transcendentals (3rd Edition)

Published by Pearson
ISBN 10: 0321999584
ISBN 13: 978-0-32199-958-0

Chapter 3 - Section 3.8 - Derivatives of Inverse Functions and Logarithms - Exercises - Page 176: 102

Answer

See screenshot of a geogebra project. Instructions and observations on each step given below. .

Work Step by Step

$CAS$ used: geogebra online (www.geogebra.org/classic). In the algebra window (to the left) enter the following: $ a.\quad$ Define $f(x)$ by entering $f(x)=\displaystyle \frac{3x+2}{2x-11},\quad {-2}\leq x\leq 2$ Next cell: $f'=Derivative(f)$ Results in$\displaystyle \quad \frac{3(2x-11)-2(3x+2)}{2}$ Enter $\displaystyle \quad Simplify (\frac{3(2x-11)-2(3x+2)}{2})$ which results in $\displaystyle \frac{-37}{(2x-11)^{2}}$ We know that $f$ is one-to-one on the given interval, because it passes the horizontal line test. $ b.\quad$ $y=\displaystyle \frac{3x+2}{2x-11}$ $2xy-11y=3x+2$ $2xy-3x=11y+2$ $x(2y-3)=11y+2$ $x=\displaystyle \frac{11y+2}{2y-3}\qquad\Rightarrow f^{-1}(x)=\frac{11x+2}{2x-3}$ enter:$\quad Solve(-2\displaystyle \leq\frac{11x+2}{2x-3}\leq 2)$ to find the domain of $g=f^{-1}:\qquad [-1.14,0.27]$ Next cell, enter:$\displaystyle \quad g(x)=\frac{11x+2}{2x-3},-1.14\leq x\leq 0.27$ $ c.\quad$ Enter:$ \displaystyle \quad P=(\frac{1}{2},f(\frac{1}{2}))\quad $(results in $(0.5,-0.35)$ the point on the graph of $f$ for $x_{0}=\displaystyle \frac{1}{2}$ Enter $\quad Q=(-0.35,0.5)$ (the point on the graph of $g=f^{-1}$, symmetric to the point P) Next, enter $h:=Tangent(P,f)\quad $resulting in $y=-0.37x-0.17$ $ d.\quad$ Next, enter $ i:=Tangent((Q,g)\quad $resulting in $y=-2.7x-0.45$ (the tangent to the inverse of $f$ at the point $(f(x_{0}),x_{0})$ Note that $-2.7\times(-0.37)=1,$ which is in line with Theorem 1, by which $f^{-1}(-0.35)=\displaystyle \frac{1}{f'(0.5)}$ $ e.\quad$ Enter the equation of the identity function, $\quad y=x.$ Enter $j=Segment(P,Q)$ With right-clicks on objects in the graphing window (to the right), set colors, dashed lines and captions, so that objects are distinct upon viewing. Note that $f$ and $g=f^{-1}$ are symmetric about the line $y=x$ as are the tangents h and i.
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