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 - Page 61: 88

Answer

120$^{\circ}$ 240$^{\circ}$

Work Step by Step

1)Since cosθ is negative, θ must lie in quadrants II or III. Since the absolute value of cosθ is $\frac{1}{2}$ the reference angle, θ must be 60° 2)The quadrant II angle θ equals 180$^{\circ}$ - 60$^{\circ}$ = 120$^{\circ}$ and the quadrant III angle θ equals 180$^{\circ}$ + 60$^{\circ}$ = 240$^{\circ}$
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