Calculus 8th Edition

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

Chapter 16 - Vector Calculus - 16.9 The Divergence Theorem - 16.9 Exercises - Page 1186: 17

Answer

$\dfrac{13 \pi}{20}$

Work Step by Step

Divergence Theorem: $\iiint_Ediv \overrightarrow{F}dV=\iint_S \overrightarrow{F}\cdot d\overrightarrow{S} $ where, $div F=\dfrac{\partial P}{\partial x}+\dfrac{\partial Q}{\partial y}+\dfrac{\partial R}{\partial z}$ Here, $S$ is a closed surface and $E$ is the region inside that surface. $div F=\dfrac{\partial a}{\partial x}+\dfrac{\partial b}{\partial y}+\dfrac{\partial c}{\partial z}=\dfrac{\partial P}{\partial x}+\dfrac{\partial Q}{\partial y}+\dfrac{\partial R}{\partial z}$ or, $\dfrac{\partial (z^2 x)}{\partial x}+\dfrac{\partial (\dfrac{1}{3} y^3+\tan z)}{\partial y}+\dfrac{\partial (x^2z+y^2)}{\partial z}=z^2+y^2+x^2$ Flux through $S_1$ $=-\int_{0}^{\pi/2}\int_{0}^{1} r^2 \sin^2 \times \theta r dr d \theta=-\int_{0}^{\pi/2}\sin^2 \theta \times [d\theta [\int_{0}^{1} r^3 dr]=(-0.5) [\theta-\dfrac{\sin 2\theta}{2}]_0^{2 \pi}=-\dfrac{\pi}{4}$ ...(1) Now, Flux through $S_2$ $=\int_{0}^{\pi/2}\int_0^{2 \pi} \int_{0}^{1} \rho^2 (\rho^2 \sin \phi) d \rho d\phi d \theta=\int_{0}^{\pi/2}\int_0^{2 \pi} \int_{0}^{1} \rho^4 \sin \phi \times d \rho d\phi d \theta=[\int_{0}^{\pi/2} \sin \phi d\pi] [ \int_0^{2 \pi} d \theta ] \times [\int_0^1 \rho^4 d\rho] =\dfrac{2\pi}{5}$ ...(2) Now, from equations (1) and (2), we have Flux through $S$ $=\dfrac{2\pi}{5}-\dfrac{\pi}{4}=\dfrac{13 \pi}{20}$
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