Elementary Geometry for College Students (7th Edition)

Published by Cengage
ISBN 10: 978-1-337-61408-5
ISBN 13: 978-1-33761-408-5

Chapter 2 - Section 2.1 - The Parallel Postulate and Special Angles - Exercises - Page 87: 11a



Work Step by Step

If two parallel lines are cut by a traversal, then the pairs of opposite angles are congruent. Since we are given that lines r and s are parallel, and $\angle$2 and $\angle$3 are opposite angles, we know that $\angle$2 and $\angle$3 are congruent. Since $\angle$2=87$^{\circ}$, $\angle$3 must also be 87$^{\circ}$.
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