Calculus 10th Edition

Published by Brooks Cole
ISBN 10: 1-28505-709-0
ISBN 13: 978-1-28505-709-5

Chapter 11 - Vectors and the Geometry of Space - Review Exercises - Page 812: 67

Answer

\[\begin{align} & \left( \mathbf{a} \right)\left( 4,\frac{3\pi }{4},2 \right) \\ & \left( \mathbf{b} \right)\left( 2\sqrt{5},\frac{3\pi }{4},\arccos \left( \frac{1}{\sqrt{5}} \right) \right) \\ \end{align}\]

Work Step by Step

\[\begin{align} & \left( -2\sqrt{2},2\sqrt{2},2 \right) \\ & \left( \mathbf{a} \right)\text{We have the rectangular coordinates }\left( -2\sqrt{2},2\sqrt{2},2 \right) \\ & \left( x,y,z \right):\text{ }\left( -2\sqrt{2},2\sqrt{2},2 \right) \\ & \text{Rectangular to cylindrical} \\ & {{r}^{2}}={{x}^{2}}+{{y}^{2}}\to r=\sqrt{{{\left( -2\sqrt{2} \right)}^{2}}+{{\left( 2\sqrt{2} \right)}^{2}}}=4 \\ & \tan \theta =\frac{y}{x}\to \theta ={{\tan }^{-1}}\left( \frac{2\sqrt{2}}{-2\sqrt{2}} \right)=\frac{3\pi }{4} \\ & z=z\to z=2 \\ & \text{The cylindrical coordinates are:} \\ & \left( 4,\frac{3\pi }{4},2 \right) \\ & \\ & \left( \mathbf{b} \right)\text{We have the rectangular coordinates }\left( -2\sqrt{2},2\sqrt{2},2 \right) \\ & \left( x,y,z \right):\left( -2\sqrt{2},2\sqrt{2},2 \right) \\ & \text{Rectangular to spherical }\left( \rho ,\theta ,\phi \right) \\ & {{\rho }^{2}}={{x}^{2}}+{{y}^{2}}+{{z}^{2}}\to \rho =\sqrt{{{\left( -2\sqrt{2} \right)}^{2}}+{{\left( 2\sqrt{2} \right)}^{2}}+{{\left( 2 \right)}^{2}}}=2\sqrt{5} \\ & \tan \theta =\frac{y}{x}\to \theta ={{\tan }^{-1}}\left( \frac{2\sqrt{2}}{-2\sqrt{2}} \right)=\frac{3\pi }{4} \\ & \phi =\arccos \left( \frac{z}{\sqrt{{{x}^{2}}+{{y}^{2}}+{{z}^{2}}}} \right)\to \phi =\arccos \left( \frac{2}{2\sqrt{5}} \right) \\ & \phi =\arccos \left( \frac{1}{\sqrt{5}} \right) \\ & \text{The spherical }\left( \rho ,\theta ,\phi \right)\text{ coordinates are:} \\ & \left( 2\sqrt{5},\frac{3\pi }{4},\arccos \left( \frac{1}{\sqrt{5}} \right) \right) \\ \end{align}\]
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