Answer
1
Work Step by Step
Recall: $\cos^{2}\theta+\sin^{2}\theta=1$ where $\theta$ is any angle for which the function values are defined.
$\implies \cos^{2}(-180^{\circ})+\sin^{2}(-180^{\circ})=1$
Precalculus (6th Edition)
by Lial, Margaret L.; Hornsby, John; Schneider, David I.; Daniels, Callie
Published by
Pearson
ISBN 10:
013421742X
ISBN 13:
978-0-13421-742-0
Chapter 5 - Trigonometric Functions - 5.2 Trigonometric Functions - 5.2 Exercises - Page 519: 80
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