Calculus: Early Transcendentals 8th Edition

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

Chapter 15 - Section 15.7 - Triple Integrals in Cylindrical Coordinates - 15.7 Exercise - Page 1044: 24

Answer

$(\dfrac{8\sqrt 2-7}{6}) \pi$

Work Step by Step

$V=\int_0^{2\pi} \int_{0}^{1}\int_{r^2}^{\sqrt{2-r^2}} r dz dr d\theta$ and $x=r \cos \theta; y=r \sin \theta, z=z$ This implies that $\int_0^{2\pi} \int_{0}^{1}[rz]_{r^2}^{\sqrt{2-r^2}} \times (r dz dr d\theta) =\int_0^{2\pi} \int_{0}^{1}(r\sqrt{2-r^2}-r^3) dr d\theta$ Consider $p=2-r^2$ and $dp=-2rdr$ or, $=-\int_0^{2\pi} [\int_{2}^{1} (\dfrac{1}{2}) \sqrt p dp-\int_0^1 r^3 dr] d\theta$ or, $=\int_0^{2\pi} [\int_{1}^{2} (\dfrac{1}{2}) \sqrt p dp -\int_0^1 r^3 dr] d\theta$ or, $=\int_0^{2\pi} (\dfrac{8\sqrt 2-7}{12}) d\theta$ or, $=(\dfrac{8\sqrt 2-7}{12}) [\theta]_0^{2\pi}$ Hence, $V=(\dfrac{8\sqrt 2-7}{6}) \pi$
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