Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 8 - Polar Coordinates; Vectors - Chapter Test - Page 656: 9

Answer

symmetric with respect to the line $\theta=\frac{\pi}{2}$, may or may not be symmetric with respect to the pole and the polar axis.

Work Step by Step

1. Given $r=5sin\theta cos^2\theta$, to test symmetry with respect to the pole, replace $r$ with $-r$, we have $-r=5sin\theta cos^2\theta$ which changes the original equation, thus it may or may not be symmetric with respect to the pole. 2. To test symmetry with respect to the polar axis, replace $\theta$ with $-\theta$, we have $r=5sin(-\theta) cos^2(-\theta)$which changes the original equation, thus it may or may not be symmetric with respect to the polar axis. 3. To test symmetry with respect to the line $\theta=\frac{\pi}{2}$, replace $\theta$ with $\pi-\theta$, we have $r=5sin(\pi-\theta) cos^2(\pi-\theta)$ which does not change the original equation, thus it is symmetric with respect to the line $\theta=\frac{\pi}{2}$.
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