Algebra 2 (1st Edition)

Published by McDougal Littell
ISBN 10: 0618595414
ISBN 13: 978-0-61859-541-9

Chapter 14 Trigonometric Graphs, Identities, and Equations - Chapter Review - Page 968: 34



Work Step by Step

Using the given identities and the known values: $\cos (3\pi/4)=\pm\sqrt{\frac{1+\cos(3\pi/2)}{2}}=-\sqrt{\frac{1+0}{2}}=-\frac{1}{\sqrt2}$
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