Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 10 - Parametric Equations and Polar Coordinates - 10.3 Polar Coordinates - 10.3 - Page 707: 55

Answer

$TLS\vert_{\frac{\pi}{3}}=\frac{1}{\sqrt{3}}$

Work Step by Step

Given: $r=2cos(\theta)$ $\theta=\frac{\pi}{3}$ Use the equation for tangent line slope for polar coordinates: $TLS=\frac{\frac{dr}{d\theta}sin\theta+rcos\theta}{\frac{dr}{d\theta}cos\theta-rsin\theta}$ Find $\frac{dr}{d\theta}$: $\frac{dr}{d\theta}=(2cos\theta)^\prime=-2sin\theta$ Plug in for $r$, $\theta$, and $\frac{dr}{d\theta}$ and evaluate: $TLS\vert_{\frac{\pi}{3}}=\frac{(-2sin\frac{\pi}{3})sin\frac{\pi}{3}+(2cos\frac{\pi}{3})cos\frac{\pi}{3}}{(-2sin\frac{\pi}{3})cos\frac{\pi}{3}-(2cos\frac{\pi}{3})sin\frac{\pi}{3}}=\frac{-2(\frac{\sqrt{3}}{2})^2+2(\frac{1}{2})^2}{(-4(\frac{\sqrt{3}}{2}))(\frac{1}{2})}$ Simplify: $TLS\vert_{\frac{\pi}{3}}=\frac{1}{\sqrt{3}}$
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