Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 11: Parametric Equations and Polar Coordinates - Section 11.4 - Graphing Polar Coordinate Equations - Exercises 11.4 - Page 666: 6

Answer

Symmetric about the y-axis. No symmetry about the x-axis. No symmetry about the origin. .

Work Step by Step

Testing for symmetry: - about the x-axis: $(r,\theta)$ on the graph $\Rightarrow (r, -\theta)$ or $(-r, \pi-\theta)$ on the graph. - about the y-axis: $(r,\theta)$ on the graph $\Rightarrow (r, \pi-\theta)$ or $(-r, -\theta)$ on the graph. - about the origin: $(r,\theta)$ on the graph $\Rightarrow (-r, \theta)$ or $(r, \theta+\pi)$ on the graph. - about the x-axis: $1+2\sin(-\theta)=1-2\sin\theta\neq r,\quad(r, -\theta)$ is not on the graph. $1+2\sin(\pi-\theta)=1+2\sin\theta=r\neq-r,\quad(-r, \pi-\theta)$ is not on the graph. No symmetry about the x-axis. - about the y-axis: $1+2\sin(\pi-\theta)=1+2\sin\theta=r,\quad(r, \pi-\theta)$ is on the graph. Symmetric about the y-axis. So, no symmetry about the origin. To graph, select a few values for $\theta$ and calculate $r.$ Use the symmetry. See the resulting image.
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