Trigonometry (10th Edition)

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

Chapter 1 - Trigonometric Functions - Section 1.3 Trigonometric Functions - 1.3 Exercises: 93

Answer

0

Work Step by Step

1. Distribute $\cos[180^{\circ}n+90^{\circ}]$ 2. If n is an integer, then all possible angles are coterminal with either 90 or 270 degree angles. Therefore: $\cos90^{\circ}=\cos270^{\circ}=0$
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