Calculus: Early Transcendentals 8th Edition

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

Chapter 15 - Section 15.8 - Triple Integrals in Cylindrical Coordinates - 15.8 Exercise - Page 1050: 20

Answer

$\int_{\pi/2}^{2\pi}\int_{0}^{\pi/2} \int_1^{2}f(\rho \sin \phi \cos \theta, \rho \sin \phi \sin \theta, \rho \cos \phi) \rho^2 \sin \phi d\rho d\phi d\theta$

Work Step by Step

In the spherical coordinates system, we have $x=\rho \sin \phi \cos \theta; y=\rho \sin \phi \sin \theta;z=\rho \cos \phi$ and $\rho=\sqrt {x^2+y^2+z^2}$; and $ \phi =\cos^{-1}(\dfrac{z}{\rho})$; $ \theta=\cos^{-1} (\dfrac{x}{\rho \sin \phi})$ In the cylindrical coordinate system, we have $r^2=x^2+y^2 ; \theta=\arctan(\dfrac{y}{x})$ and $x=r \cos \theta; y=r \sin \theta, z=z$ Consider the given integral $\iiint f(x,y,z) dz r dr d\theta=\iiint f(\rho \sin \phi \cos \theta, \rho \sin \phi \sin \theta, \rho \cos \phi) \rho^2 \sin \phi d\phi d\rho d\theta$ Now, use the boundaries in order to get the triple integration. $\iiint f(\rho \sin \phi \cos \theta, \rho \sin \phi \sin \theta, \rho \cos \phi) \rho^2 \sin \phi d\phi d\rho d\theta= \int_{\pi/2}^{2\pi}\int_{0}^{\pi/2} \int_1^{2}f(\rho \sin \phi \cos \theta, \rho \sin \phi \sin \theta, \rho \cos \phi) \rho^2 \sin \phi d\rho d\phi d\theta$
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