Trigonometry 7th Edition

Published by Cengage Learning
ISBN 10: 1111826854
ISBN 13: 978-1-11182-685-7

Chapter 3 - Section 3.1 - Reference Angle - 3.1 Problem Set - Page 122: 53

Answer

$198^{\circ}$

Work Step by Step

Given- $\sin\theta$ = - $0.3090$ , $\theta$ belongs to Q III We will find reference angle of $\theta$ first, using calculator in degree mode by the $\sin^{-1}$ key with the positive value $0.3090$- $0.3090$ → $\sin^{-1}$→→ 17.998976188 i.e. reference angle of $\theta$ = $18^{\circ}$ (to the nearest degree) The desired angle $\theta$ is in Q III, whose reference angle is $18^{\circ}$. Therefore- $\theta$ = $ 180^{\circ} + 18^{\circ}$ = $198^{\circ}$
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