Answer
$28.6^{\circ} $
Work Step by Step
We use the Law of Cosines to find:
$cos(2\alpha)= \frac{-(6^2) + 5^2 + 7^2 }{2(5)(7)} \\ cos2\alpha = .54 \\ \alpha = 28.6^{\circ} $
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: 28
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