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 562: 78

Answer

$\frac{1-\cos 2x}{\sin 2x}=\tan x$

Work Step by Step

Start with the left side: $\frac{1-\cos 2x}{\sin 2x}$ Use the double-angle formulas $\cos 2x=1-2\sin^2 x$ and $\sin 2x=2\sin x\cos x$ to expand the expression: $=\frac{1-(1-2\sin^2 x)}{2\sin x\cos x}$ Simplify: $=\frac{1-1+2\sin^2 x}{2\sin x\cos x}$ $=\frac{2\sin^2 x}{2\sin x\cos x}$ $=\frac{\sin x}{\cos x}$ $=\tan x$ Since this equals the right side, the identity is proven.
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