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: 71



Work Step by Step

Substitute $\frac{\pi}{6}$ to $x$ to obtain: $\frac{1}{2}\cos{(2x)}= \frac{1}{2}\cos{[2(\frac{\pi}{6})]}=\frac{1}{2}\cos{(\frac{\pi}{3})}$ $\dfrac{\pi}{3}$ is a special angle whose cosine value is $\dfrac{1}{2}$. Thus, when $x=\frac{\pi}{6}$, $\dfrac{1}{2}\cos{(2x)} = \dfrac{1}{2} \cdot \dfrac{1}{2}=\dfrac{1}{4}$
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