# The Sum of the Interior Angles of a Triangle Equals 180 Degrees by Paper Folding

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In high school geometry, various manipulatives (in class demonstrations, etc.) are used to show that the sum of the interior angles of a triangle equals 180 degrees. One simple example is to have the students cut off the three angles of a paper triangle and then rearrange these so that they all share a common vertex. The result is a visual proof that the sum is 180 degrees.

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Contributed by: Sean G. Corcoran (Virginia Tech) (March 2011)

Open content licensed under CC BY-NC-SA