Answer
See below.
Work Step by Step
He missed the case when $\sin\theta=0$ (when dividing). This gives an additional solution of $\theta=0$.
Algebra 2 (1st Edition)
by Larson, Ron; Boswell, Laurie; Kanold, Timothy D.; Stiff, Lee
Published by
McDougal Littell
ISBN 10:
0618595414
ISBN 13:
978-0-61859-541-9
Chapter 14 Trigonometric Graphs, Identities, and Equations - 14.4 Solve Trigonometric Equations - 14.4 Exercises - Skill Practice - Page 935: 22
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