Trigonometry (11th Edition) Clone

Published by Pearson
ISBN 10: 978-0-13-421743-7
ISBN 13: 978-0-13421-743-7

Chapter 7 - Review Exercises - Page 349: 2



Work Step by Step

The law of sines in the case of this question is: $\frac{a}{\sin A}=\frac{b}{\sin B}$ We substitute the values of $a,b$ and $A$ in the formula to find $A$: $\frac{a}{\sin A}=\frac{b}{\sin B}$ $\frac{127}{\sin 129.7}=\frac{69.8}{\sin A}$ $\sin A\times127=69.8\times \sin 129.7$ $\sin A=\frac{69.8\times \sin 129.7}{127}$ We use a calculator to find the value of $\sin 129.7$: $\sin A=\frac{69.8\times \sin 129.7}{127}$ $\sin A=\frac{69.8\times 0.76940}{127}$ $\sin A=0.422867$ $A=\sin^{-1} 0.422867$ $A=25.02\approx25.0$ Therefore, $A=25.0^{\circ}$.
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