Trigonometry 7th Edition

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

Chapter 6 - Section 6.1 - Solving Trigonometric Equations - 6.1 Problem Set - Page 325: 18

Answer

a) $194.5^{\circ} + 360^{\circ}k$ and $345.5^{\circ} + 360^{\circ}k$, for all integers $k$. b) $\theta = 194.5˚, 345.5˚$.

Work Step by Step

b) $4sin\theta + 3 = 0$ $4sin\theta = -3$ $sin\theta = -\frac{3}{4}$ There are two answers in QIII and QIV as $sin\theta$ is negative in both of those quadrants. We first get the angle of $\theta = sin^{-1}(-\frac{3}{4}) = -14.5˚$, but we'll use $14.5˚$ as the reference angle. Knowing that $sin\theta$ is negative, we only look at QIII and QIV. QIII: $\theta = 180 + 14.5$ $\theta = 194.5˚$ QIV: $\theta = 360 - 14.5$ $\theta = 345.5˚$ Therefore, $\theta = 194.5˚, 345.5˚$. a) Take the two angles and add $360^{\circ}k$for all integers $k$, to find all degree solutions. $194.5^{\circ} + 360^{\circ}k$ and $345.5^{\circ} + 360^{\circ}k$, for all integers $k$.
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