Answer
α = 50.7°
Work Step by Step
using theorem 11.4.3 Law of cosine
cos α = $\frac{5^{2} + 9^{2} - 7^{2}}{2(5)(9)}$
cos α =$\frac{25 + 81 - 49}{90}$
cos α =0.6333
α = $cos^{-1}$(0.6333)
α = 50.7°
Elementary Geometry for College Students (6th Edition)
by Alexander, Daniel C.; Koeberlein, Geralyn M.
Published by
Brooks Cole
ISBN 10:
9781285195698
ISBN 13:
978-1-28519-569-8
Chapter 11 - Section 11.4 - Applications with Acute Triangles - Exercises - Page 520: 23
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