## Trigonometry 7th Edition

Published by Cengage Learning

# Chapter 3 - Section 3.2 - Radians and Degrees - 3.2 Problem Set - Page 133: 70

#### Answer

$0$

#### Work Step by Step

Substitute $\frac{\pi}{6}$ to $x$ to obtain: $\cos{(3x)}= \cos{[3(\frac{\pi}{6})]}=\cos{(\frac{\pi}{2})}$ $\dfrac{\pi}{2}$ is a special angle whose cosine value is $0$. Thus, when $x=\frac{\pi}{6}$, $\cos{(3x)} = 0$

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