Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 8 - Application of Trigonometry - Test - Page 843: 8

Answer

Case 1. $B\approx58.5^\circ$, $A\approx 83.0^\circ$, $a \approx1250\ in$ Case 2. $B\approx121.5^\circ$, $A\approx 20.0^\circ$, $a \approx431\ in$

Work Step by Step

1. Given $b=1075\ in, c=785\ in, C=38^\circ30'=38.5^\circ$, use the Law of Sines, we have: $\frac{sinB}{1075}=\frac{sin38.5^\circ}{785}$ which gives $sinB\approx0.8525$ and $B=asin(0.8525)\approx58.5^\circ$ or $121.5^\circ$ 2. For $B\approx58.5^\circ$, we have $A\approx180^\circ-38.5^\circ-58.5^\circ=83^\circ$. Use the Law of Sines again, we have $a=\frac{c\ sinA}{sinC }=\frac{785\ sin83^\circ}{sin38.5^\circ }\approx1250\ in$ 3. For $B\approx121.5^\circ$, we have $A\approx180^\circ-38.5^\circ-121.5^\circ=20^\circ$. Use the Law of Sines again, we have $a=\frac{c\ sinA}{sinC }=\frac{785\ sin20^\circ}{sin38.5^\circ }\approx431\ in$
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