Calculus: Early Transcendentals 8th Edition

Published by Cengage Learning
ISBN 10: 1285741552
ISBN 13: 978-1-28574-155-0

Chapter 7 - Section 7.1 - Integration by Parts - 7.1 Exercises - Page 477: 64

Answer

$\displaystyle{V=9\pi\ln3-4\pi}\\$

Work Step by Step

$\displaystyle{y=e^{x}}\\ \displaystyle{\ln y=\ln e^{x}}\\ \displaystyle{\ln y=x\ln e}\\ \displaystyle{x=\ln y}$ $\displaystyle{V=\int_1^3 (2\pi y)\left(\ln y\right)\ dy}\\ \displaystyle{V=2\pi\int_1^3 y\ln y\ dx}\\$ $\displaystyle \left[\begin{array}{ll} u=\ln y & dv=y \\ & \\ du=\frac{1}{y} & v=\frac{1}{2}y^2 \end{array}\right]$ Integration by parts $\displaystyle{V=2\pi\left[\frac{1}{2}y^2\ln y\right]_1^3-2\pi\int_1^3\frac{1}{2}y^2\times\frac{1}{y}\ dy}\\ \displaystyle{V=2\pi\left[\frac{9}{2}\ln3\right]-\pi\int_1^3y\ dy}\\ \displaystyle{V=9\pi\ln3-\pi\left[\frac{1}{2}y^2\right]_1^3}\\ \displaystyle{V=9\pi\ln3-4\pi}\\$
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