Precalculus (6th Edition)

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

Chapter 8 - Application of Trigonometry - Chapter 8 Test Prep - Review Exercises - Page 838: 20

Answer

$$A = 47.65^\circ ,\,\,B = 73.96^\circ ,\,\,\,C = 58.39^\circ $$

Work Step by Step

$$\eqalign{ & a = {\text{94}}.{\text{6 yd}},b = {\text{123 yd}},c = {\text{1}}0{\text{9 yd}} \cr & \cr & {\text{Use the Law of cosines to find any Angle}} \cr & {c^2} = {a^2} + {b^2} - 2ab\cos C \cr & \cos C = \frac{{{a^2} + {b^2} - {c^2}}}{{2ab}} \cr & \cos C = \frac{{{{\left( {{\text{94}}.{\text{6}}} \right)}^2} + {{\left( {{\text{123}}} \right)}^2} - {{\left( {109} \right)}^2}}}{{2\left( {{\text{94}}.{\text{6}}} \right)\left( {{\text{123}}} \right)}} \cr & {\text{Use a calculator}} \cr & \cos C \approx 0.5241221059 \cr & C \approx {\cos ^{ - 1}}\left( {0.5241221059} \right) \cr & C \approx 58.39^\circ \cr & \cr & {\text{Calculate the angle }}A{\text{ using the law of sines}} \cr & \frac{{\sin A}}{a} = \frac{{\sin C}}{c} \cr & \sin A = \frac{{a\sin C}}{c} \cr & \sin A = \frac{{{\text{94}}.{\text{6}}\sin \left( {58.39^\circ } \right)}}{{{\text{1}}0{\text{9}}}} \cr & {\text{Use a calculator}} \cr & \sin A = 0.7391258285 \cr & A \approx {\sin ^{ - 1}}\left( {0.7391258285} \right) \cr & A \approx 47.65^\circ \cr & \cr & {\text{Calculate }}B \cr & B = {180^ \circ } - A - C \cr & B = {180^ \circ } - 47.65^\circ - 58.39^\circ \cr & B = 73.96^\circ \cr & \cr & {\text{Answer}} \cr & A = 47.65^\circ ,\,\,B = 73.96^\circ ,\,\,\,C = 58.39^\circ \cr} $$
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