## Precalculus (6th Edition) Blitzer

Published by Pearson

# Chapter 6 - Section 6.7 - The Dot Product - Exercise Set - Page 799: 47

#### Answer

a. symmetric with respect to the polar axis. b. may not be symmetric with respect to the line $\theta=\frac{\pi}{2}$. c. may not be symmetric with respect to the pole.

#### Work Step by Step

a. Given $r=5+3cos\theta$. To test the symmetry with respect to the polar axis, replace $(r,\theta)$ with $(r,-\theta)$. We have $r=5+3cos(-\theta)$, which gives $r=5+3cos\theta$. Thus the equation is symmetric with respect to the polar axis. b. To test the symmetry with respect to the line $\theta=\frac{\pi}{2}$, replace $(r,\theta)$ with $(-r,-\theta)$. We have $-r=5+3cos(-\theta)$, which gives $r=-5-3cos\theta$. Thus the equation may not be symmetric with respect to the line $\theta=\frac{\pi}{2}$. c. To test the symmetry with respect to the pole, replace $(r,\theta)$ with $(-r,\theta)$. We have $-r=5+3cos(\theta)$, which gives $r=-5-3cos\theta$. Thus the equation may not be symmetric with respect to the pole.

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