Precalculus (6th Edition)

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

Chapter 6 - The Circular Functions and Their Graphs - 6.2 The Unit Circle and Circular Functions - 6.2 Exercises - Page 588: 53


$\approx 2.3$ radians

Work Step by Step

To approximate the angle whose cosine value is $-0.65$, look up in the given figure the above $x=-0.65$. Notice that the angle that corresponds to $x=-0.65$ is between 2.2 and 2.4 radians. Thus, $\color{blue}{\cos{2.3} \approx -0.65}$
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