Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 13 - Vector Functions - 13.3 Arc Length and Curvature - 13.3 Exercises - Page 908: 31

Answer

$\kappa (x)$ has maximum at $(-\frac{1}{2} \ln 2,\frac{1}{\sqrt 2})$ and curvature approaches to $0$ ($\to 0$ ) as $x \to 0$

Work Step by Step

As we are given that $y=e^x$ Let us consider $f(x)=y=e^x$ Write formula 11. Now, $\kappa(x)=\dfrac{|f''(x)|}{[1+(f'(x))^2]^{3/2}}$ $f'(x)=e^x$ and $f''(x)=e^x$ Thus, $\kappa(x)=\dfrac{|e^x|}{[1+(e^x)^2]^{3/2}}=\dfrac{e^x}{(1+e^{2x})^{3/2}}$ Since, $\kappa'(x)=\dfrac{e^x}{(1+e^{2x})^{5/2}}(1-2e^{2x})$ Hence, $\kappa (x)$ has maximum at $(-\frac{1}{2} \ln 2,\frac{1}{\sqrt 2})$ and curvature approaches to $0$ ($\to 0$ ) as $x \to 0$
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