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: 5

Answer

Half-cone

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 $\theta=\dfrac{\pi}{3}$ $ \phi =\cos (\dfrac{\pi}{3})=\dfrac{1}{2}$; $\theta=\cos^{-1}[\dfrac{x}{\rho \sin \phi}]=\cos^{-1}\dfrac{0}{2 \sin \dfrac{\pi}{6}}=0$ Now, we have $\rho^2 \cos^2 \phi =\dfrac{1}{4}\rho^2$ This gives: $z^2=\dfrac{1}{4}(x^2+y^2+z^2)$ and $3z^2=x^2+y^2$ Thus, this is the equation for the half cone.
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