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 2.5 - Convex Polygons - Exercises - Page 116: 43



Work Step by Step

m$\angle$A+m$\angle$B+m$\angle$C+m$\angle$D=360$^{\circ}$ 20+88+31+m$\angle$D=360 m$\angle$D=221$^{\circ}$
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