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 11.7 - Conics in Polar Coordinates - Exercises 11.7 - Page 686: 37

Answer

Graph: .

Work Step by Step

The polar equation for a conic with eccentricity $e$ is $r=\displaystyle \frac{ke}{1+e\cos\theta},$ where $x=k \gt 0$ is the vertical directrix, and $\left\{\begin{array}{ll} e=1 & \Rightarrow\text{parabola}\\ e \lt 1 & \Rightarrow\text{ellipse}\\ e \gt 1 & \Rightarrow\text{hyperbola} \end{array}\right.$ Here, $e=1 \Rightarrow$ this is a parabola $k=1, \Rightarrow$ directrix: $x=1$ (opens left, since the focus is at the origin) The vertex is at $\theta=0\quad $(the x-axis). $r=\displaystyle \frac{1}{1+1}=\frac{1}{2}$ The polar coordinates of the vertex are: $(\displaystyle \frac{1}{2},0)$
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