Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 5 - Trigonometric Functions - 5.3 Trigonometric Functions Values and Angle Measures - 5.3 Exercises - Page 533: 98

Answer

$ 30^{\circ}$ and $330^{\circ}$.

Work Step by Step

The value of $\cos \theta$ is positive, so $\theta$ may lie in either quadrant I or IV. We know that $\cos 30^{\circ}=\frac{\sqrt 3}{2}$. $30^{\circ}$ is in the first quadrant. We can find the value of $\theta$ in the fourth quadrant using the identity $\cos x=\cos (360^{\circ}-x)$ $\implies \cos 30^{\circ}= \cos(360^{\circ}-30^{\circ})=\cos 330^{\circ}$ The values of $\theta$ are $ 30^{\circ}$ and $330^{\circ}$.
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.