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: 42


The concave quadrilateral ABCD has interiors angles with a sum of 360$^{\circ}$ because it is made up of two triangles whose sum of interior angles are always $180^{\circ}$.

Work Step by Step

Draw a line from B to D to form triangles BCD and ABD. Add the interior angles of each (180+180) to equal 360 for the total sum of the measures of the interior angles of the quadrilateral.
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