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 - 14.6 Apply Sum and Difference Formulas - 14.6 Exercises - Skill Practice - Page 952: 9



Work Step by Step

Using the given formula and the known values: $\cos(-\frac{5\pi}{12})=\cos(-\pi/6)\cos(-\pi/4)-\sin(-\pi/6)\sin(-\pi/4)=\frac{\sqrt3}{2}\frac{1}{\sqrt2}-\frac{1}{2}\frac{1}{\sqrt2}=\frac{\sqrt3-1}{2\sqrt2}$
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