Algebra and Trigonometry 10th Edition

Published by Cengage Learning
ISBN 10: 9781337271172
ISBN 13: 978-1-33727-117-2

Chapter 7 - 7.5 - Multiple-Angle and Product-to-Sum Formulas - 7.5 Exercises - Page 548: 19



Work Step by Step

$sin^2x+cos^2x=1$ $cos^2x=1-sin^2x$ Use: $cos~2x=cos^2x-sin^2x=1-2~sin^2x$ $4-8~sin^2x=4(1-2~sin^2x)=4~cos~2x$
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