Trigonometry 7th Edition

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

Chapter 7 - Section 7.2 - The Law of Cosines - 7.2 Problem Set - Page 378: 3

Answer

side-cosines-sines-smaller

Work Step by Step

Given $b$ and $c$ and the angle between them $A$, we get the missing side : $$a^2 =b^2+c^2-2ab \cos{A}$$ We then solve for the angle that is not opposite the largest side since it has to be acute (oblique triangle has one obtuse angle at most). Assuming $c$ is the largest side, from the law of sines: $$\sin{B} = \dfrac{b \sin{A}}{a}$$
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