Answer
True
Work Step by Step
$\cos 70^{\circ} = 0.3420201433$
$\cos 35^{\circ}\times 2 = 2\cos^{2} 35^{\circ} -1 $
$\cos 70^{\circ} = 2\cos^{2} 35^{\circ} -1 = 1.3420201433 -1 = 0.3420201433 $
Trigonometry (10th Edition)
by Lial, Margaret L.; Hornsby, John; Schneider, David I.; Daniels, Callie
Published by
Pearson
ISBN 10:
0321671775
ISBN 13:
978-0-32167-177-6
Chapter 2 - Acute Angles and Right Triangles - Section 2.3 Finding Trigonometric Function Values Using a Calculator - 2.3 Exercises - Page 64: 50
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