Calculus: Early Transcendentals 8th Edition

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

Chapter 6 - Section 6.2 - Volume - 6.2 Exercises - Page 446: 13

Answer

$\displaystyle{V=2\pi\left(\frac{4\pi }{3}-\sqrt{3}\right)}\\ $

Work Step by Step

$\displaystyle{3=1+\sec x}\\ \displaystyle{\sec x=2}\\ \displaystyle{\cos x=\frac{1}{2}}\\ \displaystyle{x=-\frac{\pi}{3} \qquad x=\frac{\pi}{3}}$ $\displaystyle{A\left(x\right)=\pi \left(1-3\right)^2-\pi \left(1-\left(1+\sec x\right)\right)^2}\\ \displaystyle{A\left(x\right)=\pi \left(4-\sec^2x\right)}\\$ $\displaystyle{V=\int_{-\frac{\pi}{3}}^{\frac{\pi}{3}}A\left(x\right)\ dx}\\ \displaystyle{V=\int_{-\frac{\pi}{3}}^{\frac{\pi}{3}}\pi \left(4-\sec^2x\right)\ dx}\\ \displaystyle{V=\pi \int_{-\frac{\pi}{3}}^{\frac{\pi}{3}}4-\sec^2x\ dx}\\$ By symmetry $\displaystyle{V=2\pi \int_{0}^{\frac{\pi}{3}}4-\sec^2x\ dx}\\ \displaystyle{V=2\pi\left[4x-\tan x\right]_{0}^{\frac{\pi}{3}}}\\ \displaystyle{V=2\pi\left(\left(4\times\left({\frac{\pi}{3}}\right)-\tan \left({\frac{\pi}{3}}\right)\right)-\left(4(0)-\tan (0)\right)\right)}\\ \displaystyle{V=2\pi\left(\frac{4\pi }{3}-\sqrt{3}\right)}\\ $
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