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 7.3 - Exponential Functions - Exercises 7.3 - Page 392: 128

Answer

${\pi(\frac{15}{16}+\ln2)}$

Work Step by Step

$\frac{dx}{dy}$ = $\frac{1}{2}(e^{y}-e^{-y})$ $S$ = $\int_{{\,0}}^{{\,\ln2}}$$2\pi({\frac{1}{2})(e^{y}+e^{-y})}\sqrt {1+(\frac{1}{2}(e^{y}-e^{-y}))^{2}}$$dy$ $S$ = $\int_{{\,0}}^{{\,\ln2}}$${\pi(e^{y}+e^{-y})}\sqrt {1+\frac{1}{4}e^{2y}-\frac{1}{2}+\frac{1}{4}e^{-2y}}$ $dy$ $S$ = $\int_{{\,0}}^{{\,\ln2}}$${\pi(e^{y}+e^{-y})}\sqrt {\frac{1}{4}e^{2y}+\frac{1}{2}+\frac{1}{4}e^{-2y}}$ $dy$ $S$ = $\int_{{\,0}}^{{\,\ln2}}$${\pi(e^{y}+e^{-y})}\sqrt{(\frac{1}{2}e^{y}+\frac{1}{2}e^{-y})^{2}}$ $dy$ $S$ = $\int_{{\,0}}^{{\,\ln2}}$${\frac{\pi}{2}(e^{y}+e^{-y})(e^{y}+e^{-y})}$$dy$ $S$ = $\int_{{\,0}}^{{\,\ln2}}$${\frac{\pi}{2}(e^{2y}+2+e^{-2y})}$$dy$ $S$ = ${\frac{\pi}{2}(\frac{1}{2}e^{2y}+2y-\frac{1}{2}e^{-2y})}$$|_{{\,0}}^{{\,\ln2}}$ $S$ = ${\frac{\pi}{2}[(2+2\ln2-\frac{1}{8})-(\frac{1}{2}+0-\frac{1}{2})]}$ $S$ = ${\frac{\pi}{2}(\frac{15}{8}+2\ln2)}$ $S$ = ${\pi(\frac{15}{16}+\ln2)}$
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