Trigonometry (10th Edition)

Published by Pearson
ISBN 10: 0321671775
ISBN 13: 978-0-32167-177-6

Chapter 5 - Trigonometric Identities - Section 5.1 Fundamental Identities - 5.1 Exercises - Page 194: 23

Answer

$$\cos(-\theta)=\cos\theta$$

Work Step by Step

From the Negative-Angle Identities, we know that $$\cos(-\theta)=\cos\theta$$ Therefore, we should fill in the blank with $\cos\theta$.
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