Trigonometry 7th Edition

Published by Cengage Learning
ISBN 10: 1111826854
ISBN 13: 978-1-11182-685-7

Chapter 5 - Section 5.5 - Additional Identities - 5.5 Problem Set - Page 311: 21

Answer

$2x^2 -1$

Work Step by Step

$\theta = \cos^{-1}{x} $ $\cos{\theta} = x$ $\cos{2\theta} = 2\cos^2{\theta} -1 = 2x^2 -1$
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