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: 7

Answer

Negative sign

Work Step by Step

$\theta =195\left( Q3;180 < \theta < 270\right) $ So if angle is in quadrant 3 we should choose negative sign
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