Trigonometry (10th Edition)

Published by Pearson
ISBN 10: 0321671775
ISBN 13: 978-0-32167-177-6

Chapter 7 - Review Exercises - Page 343: 17

Answer

The angles of the triangle are as follows: $A = 25.2^{\circ}, B = 17.3^{\circ},$ and $C = 137.5^{\circ}$ The lengths of the sides are as follows: $a = 6.92~yd, b = 4.82~yd,$ and $c = 10.98~yd$

Work Step by Step

$A = 25.2^{\circ}$ $a = 6.92~yd$ $b = 4.82~yd$ We can use the law of sines to find angle $B$: $\frac{a}{sin~A} = \frac{b}{sin~B}$ $sin~B = \frac{b~sin~A}{a}$ $B = arcsin(\frac{b~sin~A}{a})$ $B = arcsin(\frac{4.82~sin~25.2}{6.92})$ $B = arcsin(0.29657)$ $B = 17.3^{\circ}$ We can find angle $C$: $A+B+C = 180^{\circ}$ $C = 180^{\circ}-A-B$ $C = 180^{\circ}-25.2^{\circ}-17.3^{\circ}$ $C = 137.5^{\circ}$ We can use the law of sines to find the length of side $c$: $\frac{c}{sin~C} = \frac{a}{sin~A}$ $c = \frac{a~sin~C}{sin~A}$ $c = \frac{(6.92~yd)~sin~(137.5^{\circ})}{sin~25.2^{\circ}}$ $c = 10.98~yd$ Note that another possible value for angle $B$ is $180^{\circ}-17.3^{\circ} = 162.7^{\circ}$ However, then the sum of angle A and angle B is greater than $180^{\circ}$, so this value for angle B is not acceptable.
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