Algebra 2 Common Core

Published by Prentice Hall
ISBN 10: 0133186024
ISBN 13: 978-0-13318-602-4

Chapter 14 - Trigonometric Identities and Equations - 14-5 The Law of Cosines - Practice and Problem-Solving Exercises - Page 939: 10

Answer

$x^{o} \approx 47.3^{o}$

Work Step by Step

Apply law of cosines $b^2=a^2+c^2-2ac \cos B$ Need to solve for $B =x^{o}$ $2ac \cos x^{o}=a^2+c^2-b^2$ This implies $x^{o}=\cos^{-1}(\dfrac{a^2+c^2-b^2}{2ac})$ Plug the given values to obtain: $x^{o}=\cos^{-1}(\dfrac{a^2+c^2-b^2}{2ac})$ $x^{o}=\cos^{-1}(\dfrac{(19)^2+(12)^2-(14)^2}{2 \times 19 \times 12})$ $x^{o}=\cos^{-1}(\dfrac{309}{456})$ In order to calculate the value, we will use calculator in degree mode. $x^{o} \approx 47.3^{o}$
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