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: 64

Answer

$cos (-90^{\circ})=0$

Work Step by Step

1. What we know about -90 degree angle $\theta=270^{\circ}$ (because it is a co-terminal angle and values of x and y will be the same) $x=0$ $y=-1$ $r=1$ 2. Substitute in: $\cos\theta=\frac{x}{r}=\frac{0}{1}=0$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.