I recently wrote a post about Crockett Johnson’s *neusis* construction of a regular heptagon. Johnson’s proof that the construction was correct required heavy trigonometry. I asked if there was a geometric proof that didn’t use trigonometry.

My friend Dan Lawson came to the rescue—he posted the following lovely proof on Twitter. Thanks Dan!

[…] Dan Lawson has proved the theorem without trigonometry. Thanks, […]

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A Geometry Theorem Looking for a Geometric Proof | Division by Zeroon April 7, 2016at 2:04 pm