Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 7 - Section 7.4 - Basic Trigonometric Equations - 7.4 Exercises - Page 569: 29

Answer

$0.20+2k\pi$, $2.94+2k\pi$

Work Step by Step

$\begin{align} 5\sin\theta-1&=0\\ 5\sin\theta&=1\\ \sin\theta&=\frac{1}{5} \end{align}$ Since $\sin \theta$ is positive in the first and second quadrants, the only values of $\theta$ between $0$ and $2\pi$ that satisfy the equation are $0.20$ and $\pi-0.20\approx 2.94$. Since $\sin \theta$ is a periodic function with period $2\pi$, we can add or subtract any multiple of $2\pi$ from $0.20$ or $2.94$ and the equation would still be satisfied. So the answers are $0.20+2k\pi$ and $2.94+2k\pi$ for any integer $k$.
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