Trigonometry (10th Edition)

Published by Pearson
ISBN 10: 0321671775
ISBN 13: 978-0-32167-177-6

Chapter 2 - Acute Angles and Right Triangles - Section 2.2 Trigonometric Functions of Non-Acute Angles - 2.2 Exercises: 39

Answer

$\cos$ -510$^{\circ}$ = $\frac{-\sqrt3}{2}$

Work Step by Step

$\cos$ -510$^{\circ}$ First, lets find the coterminal angle. -510$^{\circ}$ - 360$^{\circ}$ = -150$^{\circ}$ Next, we find the reference angle. $\theta$$^{1}$ = 180$^{\circ}$ - 150$^{\circ}$ = 30$^{\circ}$ Since the coterminal angle is in Quadrant III, $\cos$ is negative. Therefore: $\cos$ 30$^{\circ}$ = $\frac{-\sqrt3}{2}$
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