# Geometry: Properties of All Quadrilaterals

## Properties of All Quadrilaterals

Quadrilaterals: The shape of books, envelopes, picture frames, and more. Let's think about the properties that all quadrilaterals possess.

First of all, all quadrilaterals have four sides. There is no such thing as a three-sided quadrilateral. Don't confuse a three-sided quadrilateral with a three-sided polygon. A three-sided polygon is called a triangle, and you just spent several chapters exploring its properties. A three-sided quadrilateral does not exist, even in the twilight zone.

Every quadrilateral has two diagonals, and the sum of the measures of the interior angles is 360º.

Now it's time to explore the properties of the various types of quadrilaterals. For example, you will explore what makes a rectangle a rectangle, and not a kite. I'll start with the most general quadrilaterals and end with the most restrictive shapes.

Excerpted from The Complete Idiot's Guide to Geometry © 2004 by Denise Szecsei, Ph.D.. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.

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