Geometry: Common Core (15th Edition)

Published by Prentice Hall
ISBN 10: 0133281159
ISBN 13: 978-0-13328-115-6

Chapter 1 - Tools of Geometry - 1-5 Exploring Angle Pairs - Practice and Problem-Solving Exercises - Page 39: 35


$\angle ECD=155$

Work Step by Step

$\angle ECD$ and $\angle BCD$ are a linear pair. From exercise 34, we know $m\angle BCD$ is 25 degrees. Use the definition of a linear pair: $\angle ECD+\angle BCD=180$ $\angle ECD+25=180$ $\angle ECD+25-25=180-25$ $\angle ECD=155$
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