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: 25

Answer

$\dfrac{\pi}{8}$

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 $\rho=\sqrt {x^2+y^2+z^2} \implies \rho^2=x^2+y^2+z^2$ Now, consider $I=\int_0^{\pi/2} \int_{0}^{\pi/2}\int_{0}^{1} \times (\rho \sin \phi \cos \theta) \times e^{\rho^2} \times (\rho^2 \sin \phi) d\rho d\theta d\phi$ $=\int_0^{\pi/2} ( \sin^2 \phi d\phi) \cdot \int_{0}^{\pi/2} \cos \theta d\theta \cdot \int_{0}^{1} \rho^3 e^{\rho^2} d\rho $ Hence, $I=[\dfrac{\phi}{2}-\dfrac{\sin 2\phi}{4}]_0^{\pi/2} [\sin (\pi/2)-\sin 0] \cdot [ \dfrac{1}{2} e^{(1)^2} (1-1)- \dfrac{1}{2} e^{(0)^2} (0^2-1)]=\dfrac{\pi}{8}$
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