Precalculus (6th Edition)

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

Chapter 7 - Trigonometric Identities and Equations - 7.6 Trigonometric Equations - 7.6 Exercises - Page 721: 32



Work Step by Step

$\cos^{2}\theta-\sin^{2}\theta =1$ ... recognize a double angle (cosine) identity $\cos 2\theta=1$ If $0 \leq \theta < 360^{o}\quad/\times 2$ $0 \leq 2\theta < 720^{o}$ $ 2\theta=0^{o}\quad$ or $\quad 2\theta=360^{o}$ $\theta=0^{o}\quad$ or $\quad \theta=180^{o}$ Solution set= $\{0^{o},180^{o}\}$
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