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: 57

Answer

$\cos 90^{\circ}= 0$

Work Step by Step

1. We know about 90 degree angle $\theta=90^{\circ}$ $x=0$ $y=1$ $r=1$ 2. Substitute in: $\cos\theta=\frac{x}{r}=\frac{0}{1}=0
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