Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 13 - Vector Geometry - Chapter Review Exercises - Page 703: 61

Answer

The point in cylindrical coordinates is $\left( {r,\theta ,z} \right) = \left( {5,0.927, - 1} \right)$. The point in spherical coordinates is $\left( {\rho ,\theta ,\phi } \right) = \left( {\sqrt {26} ,0.927,1.768} \right)$.

Work Step by Step

We have $\left( {x,y,z} \right) = \left( {3,4, - 1} \right)$. 1. Convert to cylindrical coordinates. The radial coordinate is $r = \sqrt {{x^2} + {y^2}} = \sqrt {{3^2} + {4^2}} = 5$. The angular coordinate $\theta$ satisfies $\tan \theta = \frac{y}{x}$. So, $\tan \theta = \frac{4}{3}$, ${\ \ }$ $\theta \simeq 0.927$ The $z$-coordinate is the same, so $z=-1$. Thus, the point in cylindrical coordinates is $\left( {r,\theta ,z} \right) = \left( {5,0.927, - 1} \right)$. 2. Convert to spherical coordinates. The radial coordinate is $\rho = \sqrt {{x^2} + {y^2} + {z^2}} = \sqrt {{3^2} + {4^2} + {{\left( { - 1} \right)}^2}} = \sqrt {26} $ The angular coordinate $\theta$ satisfies $\tan \theta = \frac{y}{x}$. So, $\tan \theta = \frac{4}{3}$, ${\ \ }$ $\theta \simeq 0.927$ The angular coordinate $\phi$ satisfies $\cos \phi = \frac{z}{\rho } = \frac{{ - 1}}{{\sqrt {26} }}$, ${\ \ }$ $\phi = 1.768$ Thus, the point in spherical coordinates is $\left( {\rho ,\theta ,\phi } \right) = \left( {\sqrt {26} ,0.927,1.768} \right)$.
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