Calculus 8th Edition

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

Chapter 15 - Multiple Integrals - 15.8 Triple Integrals in Spherical Coordinates - 15.8 Exercises - Page 1090: 25

Answer

$\dfrac{\pi}{8}$

Work Step by Step

The conversion of rectangular coordinates to spherical coordinates is given as: $x=\rho \sin \phi \cos \theta; y=\rho \sin \phi \sin \theta;z=\rho \cos \phi$ Here, $\rho=\sqrt {x^2+y^2+z^2}$; $\phi =\cos^{-1} [\dfrac{z}{\rho}]; \theta=\cos^{-1}[\dfrac{x}{\rho \sin \phi}]$ $I=\int_0^{\pi/2} \int_{0}^{\pi/2}\int_{0}^{1} (\rho \sin \phi \cos \theta) e^{\rho^2} \times (\rho^2 \sin \phi) d\rho d\theta d\phi$ $=\int_0^{\pi/2} ( \sin^2 \phi d\phi) \times \int_{0}^{\pi/2} \cos \theta d\theta \times \int_{0}^{1} \rho^3 e^{\rho^2} d\rho $ $=(1-0) \times [\dfrac{\phi}{2}-\dfrac{\sin 2\phi}{4}]_0^{\pi/2} \times [ \dfrac{1}{2} e^{(1)^2} (1-1)- \dfrac{1}{2} e^{(0)^2} (0^2-1)]$ Hence, $I=[\dfrac{\phi}{2}-\dfrac{\sin 2\phi}{4}]_0^{\pi/2} \times [0- \dfrac{1}{2} e^{(0)^2} (0^2-1)]=\dfrac{\pi}{4}[0-\dfrac{1}{2}(-1)]=\dfrac{\pi}{8}$
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