Trigonometry 7th Edition

Published by Cengage Learning
ISBN 10: 1111826854
ISBN 13: 978-1-11182-685-7

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



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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