Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 7 - Trigonometric Identities and Equations - 7.4 Double-Angle and Half-Angle Identities - 7.4 Exercises - Page 693: 29


$\dfrac {\cos 94.2}{4}$

Work Step by Step

$1-2\sin ^{2}\alpha =\cos 2\alpha \Rightarrow \dfrac {1}{4}-\dfrac {1}{2}\sin ^{2}47.1=\dfrac {1}{4}\left( 1-2\sin ^{2}47.1\right) =\dfrac {1}{4}\cos \left( 2\times 47.1\right) =\dfrac {\cos 94.2}{4}$
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