Elementary Geometry for College Students (5th Edition)

Published by Brooks Cole
ISBN 10: 1439047901
ISBN 13: 978-1-43904-790-3

Chapter 11 - Section 11.2 - The Cosine Ratio and Applications - Exercises: 35

Answer

13.1

Work Step by Step

When we break a regular decagon into 20 separate right triangles, each triangle has an angle of 18 degrees in it. Using this angle and the fact that the apothem is 12.5 inches, we find: $cos18^{\circ}=\frac{12.5}{r} \\ r = \frac{12.5}{cos18^{\circ}} = 13.1$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.