Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 7 - Section 7.3 - Double-Angle, Half-Angle, and Product-Sum Formulas - 7.3 Exercises - Page 561: 29


a. $\sin 36^\circ$ b. $\sin 6\theta$

Work Step by Step

a. Use the formula $\sin 2x=2\sin x\cos x$ with $x=18^\circ$. Then $2\sin 18^\circ\cos 18^\circ=\sin(2*18^\circ)=\sin 36^\circ$. b. Use the formula $\sin 2x=2\sin x\cos x$ with $x=3\theta$. Then $2\sin 3\theta\cos 3\theta=\sin(2*3\theta)=\sin 6\theta$.
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