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© 1999-2010 by Francis Edward Su
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From the Fun Fact files, here is a Fun Fact at the Easy level:

Napoleon's Theorem

Figure 1
Figure 1

Take any generic triangle, and construct equilateral triangles on each side whose side lengths are the same as the length of each side of the original triangle.

Surprise: the centers of the equilateral triangles form an equilateral triangle!

Presentation Suggestions:
Show the truth of the statement using some extreme cases for the initial triangle (a particularly instructive example is a triangle with one sidelength very close to zero).

The Math Behind the Fact:
This theorem is credited to Napoleon, who was fond of mathematics, though many doubt that he knew enough math to discover it!

How to Cite this Page:
Su, Francis E., et al. "Napoleon's Theorem." Math Fun Facts. <http://www.math.hmc.edu/funfacts>.

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Subjects:    geometry
Level:    Easy
Fun Fact suggested by:   Michael Moody
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