Calculus: Early Transcendentals (2nd Edition)

Published by Pearson
ISBN 10: 0321947347
ISBN 13: 978-0-32194-734-5

Chapter 1 - Functions - 1.4 Trigonometric Functions and Their Inverse - 1.4 Exercises - Page 48: 53


$cos^{-1}(-\frac{1}{2}) = \frac{2\pi}{3}$

Work Step by Step

The domain of $cos^{-1}(x)$ is $[\frac{-\pi}{2}, \frac{\pi}{2}]$ and $x=-\frac{1}{2}$ is in the domain. Since $cos(\frac{2\pi}{3}) = -\frac{1}{2}$, $cos^{-1}(-\frac{1}{2}) = \frac{2\pi}{3}$.
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