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: 23

Answer

$\dfrac{1688 \pi}{15}$

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, $\rho=\sqrt {x^2+y^2+z^2}$; $\phi =\cos^{-1} [\dfrac{z}{\rho}]; \theta=\cos^{-1}[\dfrac{x}{\rho \sin \phi}]$ Here, we have $(x^2+y^2+z^2)=9 $ and $\rho=3$ Now, consider the integral such as: $I=\int_0^{\pi} \int_{0}^{2 \pi}\int_{2}^{3} (\rho^2 \sin^2 \phi) \times (\rho^2 \sin \phi) \times d\rho d\theta d\phi=\int_0^{\pi} \int_{0}^{2 \pi} [\dfrac{\rho^5}{5} \times \sin^3 \phi]_2^3 d\theta d\phi$ $=\dfrac{211}{5} \times \int_0^{\pi} (2 \pi \sin^3 \phi ] d\phi$ $=\dfrac{422\pi}{5} \times \int_0^{\pi} \sin \phi(1-\cos^2 \phi) d\phi$ Now, plug $\cos \phi =a $ and $ da=-\sin \phi d\phi$ $I= \dfrac{422\pi}{5} \times \int_1^{-1} 1-a^2 da=[\dfrac{422\pi}{5}][a-\dfrac{a^3}{3}]_1^{-1} =\dfrac{1688 \pi}{15}$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.