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Geometry: Two's Company, Three's a Triangle

Two's Company, Three's a Triangle

As long as there are three of anything, there will be triangles. You can find three of anything almost everywhere you look. Usually the only triangles you read about in books are love triangles. But in this there will be no tragedy; no one will be jealous and no one will get hurt.

Triangles have the distinction of being the simplest polygon in that they have the fewest number of sides. You can break up convex polygons into triangles, which is how you were able to calculate the sum of the interior angles of a polygon. When you think of basic building blocks, you usually think of rectangles, but two triangles can combine to form a rectangle.

Triangles are the shape of choice when designing the wing of a paper airplane, the flap of an envelope, or the side of a pyramid. This section gives you the opportunity to get to know them better.

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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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