Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 8 - Applications of Trigonometric Functions - 8.2 The Law of Sines - 8.2 Assess Your Understanding - Page 530: 9

Answer

$A=40°$ $a\approx3.23$ $b\approx3.55$

Work Step by Step

First, we can calculate the third angle by the rule of: $A+B+C=180^{\circ}$ Here, we have $B=45°$ $C=95°$ Therefore $A=180°-95°-45°=40°$ Now, by applying the Law of Sines we can calculate the remaining two sides: $$\dfrac{\sin(A)}{a}=\dfrac{\sin(B)}{b}=\dfrac{\sin(C)}{c}$$ We know one side of the equation, which is: $$\dfrac{\sin(C)}{c}=\dfrac{\sin(95°)}{5}$$ First, we calculate $a$: $$\dfrac{\sin(A)}{a}=\dfrac{\sin(C)}{c}\\ \dfrac{\sin(40°)}{a}=\dfrac{\sin(95°)}{5}$$ Cross-multiply, then isolate $a$ to obtain: $$a\cdot \sin95°=5\cdot\sin40°\\ a=\dfrac{5\cdot\sin40°}{\sin95°}\\ a\approx3.23$$ Next, solve for $b$: $$\dfrac{\sin(B)}{b}=\dfrac{\sin(C)}{c}\\ \dfrac{\sin(45°)}{b}=\dfrac{\sin95°}{5}$$ Cross-multiply, then isolate $b$ to obtain: $$b\cdot\sin95°=5\cdot\sin45°\\ b=\dfrac{5\cdot \sin45°}{\sin95°}\\ b\approx 3.55$$
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