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 1 - Trigonometric Functions - Section 1.3 Trigonometric Functions - 1.3 Exercises - Page 28: 106

Answer

$\cos(-x)=\cos x $

Work Step by Step

1. Set up calculator in degrees $\cos20^{\circ}\approx0.9397$ $\cos(-20)^{\circ}\approx0.9397$ 2. Pick up more examples $\cos60^{\circ}=0.5$ $cos(-60)^{\circ}=0.5$

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