Algebra and Trigonometry 10th Edition

Published by Cengage Learning
ISBN 10: 9781337271172
ISBN 13: 978-1-33727-117-2

Chapter 8 - 8.2 - Law of Cosines - 8.2 Exercises - Page 573: 12

Answer

c = 13.87 A = $43.28^{o}$ B = $28.72^{o}$

Work Step by Step

Note: The Standard Form of the Law of Cosines is: $a^{2} = b^{2} + c^{2} - 2bc(cosA)$ Note: The Alternative Form of the Law of Cosines is: $cosA = \frac{b^{2} + c^{2} - a^{2}}{2bc}$ To solve the triangle, we need to find A, B, and c. We can use the Standard and Alternative Form of the Law of Cosines to solve the triangle. Finding c: $c^{2} = 10^{2} + 7^{2} - 2(10)(7)cos(108^{o})$ c = 13.87 Finding A: $cosA = \frac{7^{2} + 13.87^{2} - 10^{2}}{2(7)(13.87)}$ A = $43.28^{o}$ Finding B: $cosB = \frac{10^{2} + 13.87^{2} - 7^{2}}{2(10)(13.87)}$ B = $28.72^{o}$ In Total: c = 13.87 A = $43.28^{o}$ B = $28.72^{o}$
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