Answer
$\cos^2{x} - \sin^2{x}$
Work Step by Step
$\cos{(2x)}=\cos{(x+x)} $
$\cos{(A+B)} = \cos{A} \cos{B} - \sin{A} \sin{B}$
$\cos{(x+x)} = \cos{x} \cos{x} - \sin{x} \sin{x} = \cos^2{x} - \sin^2{x}$
Trigonometry 7th Edition
by McKeague, Charles P.; Turner, Mark D.
Published by
Cengage Learning
ISBN 10:
1111826854
ISBN 13:
978-1-11182-685-7
Chapter 5 - Section 5.2 - Sum and Difference Formulas - 5.2 Problem Set - Page 289: 49
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