Answer
See below
Work Step by Step
We are given $a, c, b$. Use law of cosines to find $c$:
$$a^2=b^2+c^2-2bc\cos A\\ \cos A=\arccos\frac{a^2-b^2-c^2}{-2bc}\\\cos A=\frac{15^2+10^2-18^2}{-2(15)(10)} \approx 0.00333\\A\approx 89.81$$
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 13, Trigonometric Ratios and Functions - 13.6 Apply the Law of Cosines - 13.6 Exercises - Skill Practice - Page 893: 35
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