Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 7: Transcendental Functions - Section 7.1 - Inverse Functions and Their Derivatives - Exercises 7.1 - Page 374: 61

Answer

See screnshot 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 $f(x)=\displaystyle \sqrt{3x-2}, \frac{3}{2}\leq x\leq 4$ Next cell: $f'=Derivative(f)$ Results in$\displaystyle \quad \frac{3}{2}(3x-2)^{-1/2}$ We know that f is one-to-one on the given interval, because it passes the horizontal line test. $ b.\quad$ Next cell, we find the inverse of f. Enter: $g(x)=Invert(f)$ Results in$\quad \displaystyle \frac{x^{2}+2}{3}, \quad \frac{3}{2}\leq g(x)\leq 4$ $ c.\quad$ Enter:$ \quad P=(3,f(3))\quad $(results in $(3,2.65)$ The point on the graph of $f$ for $x_{0}=3$ Next, enter $h:=Tangent(P,f)$ resulting in $y=0.57x+0.94$ $ d.\quad$ Next, enter $i:=Tangent((f(3),3),g)$ resulting in $y=1.76x-1.67$, (the tangent to the inverse of f at the point $(f(x_{0}),x_{0})$ Note that $1.76\times 0.57=1,$ which is in line with Theorem 1, by which $f^{-1}(2.65)=\displaystyle \frac{1}{f'(3)}$ $ e.\quad$ Enter the equation of the identity function, $\quad y=x.$ Enter $\quad Q=(f(3),3)$ Enter $j=Segment(P,Q)$ You may want to find the domain of $g=f^{-1}$, which is $[1.58,3.16]$ found by entering$\quad Solve(\displaystyle \frac{3}{2}\leq\frac{x^{2}+2}{3}\leq 4)$ 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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