Trigonometry (10th Edition)

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: 48

Answer

False

Work Step by Step

$\cos$ 40$^{\circ}$ = 2 $cos$ 20$^{\circ}$ $\cos$ 40$^{\circ}$ $\approx$ 0.76604444 $\cos$ 20$^{\circ}$ $\approx$ 0.93969262 2 $\cos$ 20$^{\circ}$ $\approx$ 1.87938524 Therefore: $\cos$ 40$^{\circ}$ $\ne$ 2 $cos$ 20$^{\circ}$
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