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: 76

Answer

Between 0$^{\circ}$ and 360$^{\circ}$ $\cos$ $\theta$ = -$\sin$ $\theta$ is true for 135$^{\circ}$ and 315$^{\circ}$

Work Step by Step

$\theta$ = 135$^{\circ}$ $\cos$ 135$^{\circ}$ = -$\frac{\sqrt2}{2}$ $\theta$ = 315$^{\circ}$ $\sin$ 315$^{\circ}$ = $\frac{\sqrt2}{2}$ Therefore: -$\sin$ 315$^{\circ}$ = -$\frac{\sqrt2}{2}$ Therefore, $\cos$ 135$^{\circ}$ = -$\sin$ 315$^{\circ}$ Therefore: Between 0$^{\circ}$ and 360$^{\circ}$ $\cos$ $\theta$ = -$\sin$ $\theta$ is true for 135$^{\circ}$ and 315$^{\circ}$
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