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Napoleon's Theorem

© Copyright 2003, Jim Loy

Apparently Napoleon Bonaparte came up with this theorem:

On any triangle, draw equilateral triangles on each side. Then the lines connecting the centers of these equilateral triangles form another equilateral triangle (the one in red here).

This equilateral triangle is called the outer Napoleon triangle.

the inner Napoleon trianglesThe theorem also works for the inner Napoleon triangle (right, in red). Here the equilateral triangles are drawn toward the inside of the original triangle. And the area of the outer Napoleon triangle, minus the area of the inner Napoleon triangle, is equal to the area of the original triangle.

These diagrams were drawn with the program Cinderella.


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