Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 5 - Trigonometric Functions - Section 5.3 Properties of the Trigonometric Functions - 5.3 Assess Your Understanding - Page 418: 90



Work Step by Step

As $\cos(\theta+2\pi)=\cos(\theta+4\pi)=\cos\theta$, we have $\cos\theta+\cos(\theta+2\pi)+\cos(\theta+4\pi)=\cos{\theta}+\cos{\theta}+\cos{\theta}=3\cos\theta=3(0.2)=0.6$
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