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: 11

Answer

Symmetric about the y-axis. Symmetric about the x-axis. Symmetric 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: $\sin(\pi-\theta)=\sin(\theta)=r^{2},\quad(r, \pi-\theta)$ is on the graph Symmetric about the x-axis. - about the y-axis: $-\sin(\pi-\theta)=-\sin(\theta)=r^{2}=(-r)^{2},\quad(-r, \pi-\theta)$ is on the graph. Symmetric about the y-axis. So, the graph is also symmetric about the origin. To graph, select a few values for $\theta \in[\pi,3\pi/2]$ and calculate $r=\sqrt{-\sin\theta}.$ Use the symmetries. See the resulting image.
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