Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 10 - Geometry - Chapter Summary, Review, and Test - Review Exercises - Page 680: 15


$m\angle{A} = 51^o$

Work Step by Step

The sum of the three interior angles of a triangle is 180 degrees. Angle C is a right angle, so its measure is 90 degrees. Thus, $m\angle{A} + m\angle{B} + m\angle{C} = 180^o \\m\angle{A} + 90^o + 39^o = 180^o \\m\angle{A} + 129^o = 180^o \\m\angle{A} = 180^o - 129^o \\m\angle{A} = 51^o$
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.