## Calculus (3rd Edition)

Published by W. H. Freeman

# Chapter 1 - Precalculus Review - 1.4 Trigonometric Functions - Exercises - Page 30: 9

#### Answer

$\dfrac{\pi}{3}, \dfrac{5\pi}{3}$

#### Work Step by Step

Since $\cos{\theta}$= x-coordinate From figure 22, angles $\dfrac{\pi}{3}$ and $\dfrac{5\pi}{3}$ have a x-coordinate of $\dfrac{1}{2}$ on the unit circle $\theta= \dfrac{\pi}{3}, \dfrac{5\pi}{3}$

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