Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 6 - Section 6.2 - The Law of Cosines - Exercise Set - Page 730: 12

Answer

$a\approx4.3, B\approx66^\circ, C\approx14^\circ$

Work Step by Step

Step 1. Based on the given conditions, using the Law of Cosines, we have $a^2=b^2+c^2-2bc\ cosA$, or $a^2=(4)^2+(1)^2-2(4)(1)cos(100^\circ)\approx 18.39$, thus $c=\sqrt {18.39}\approx 4.3$ Step 2. Using the Law of Sines, we have $\frac{SinB}{b}=\frac{SinA}{a}$, $SinB=\frac{4}{4.3}sin(100^\circ)\approx 0.9161$, thus $B=sin^{-1}(0.9161)\approx66^\circ$ Step 3. We can find the angle as $C=180^\circ-100^\circ-66^\circ=14^\circ$ Step 4. We solved the triangle with $a\approx4.3, B\approx66^\circ, C\approx14^\circ$
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