A Geometry Theorem Looking for a Geometric Proof

[Update: Dan Lawson has proved the theorem without trigonometry. Thanks, Dan!] I spent a good chunk of last week reading about David Johnson Leisk (1906–1975), who is better known by his nom-de-plum Crockett Johnson. Johnson is most well known as the author of Harold and the Purple Crayon, a children’s book from 1955, and its sequels. Johnson was also the…

Mathematical art by Kevin Van Aelst

I just stumbled upon the website of the artist Kevin Van Aelst. His photographs are scenes constructed from food and drink that take the form of mathematical and scientific images. Here are some of the mathematical pictures on his artwork page: A Cantor set made out of fried eggs Logarithmic spiral made out of crumbs…

Symmetry groups of viral doilies

Are you looking for interesting examples to use in your abstract algebra course to illustrate planar objects with rotational and reflective symmetries? Tired of the usual regular polygons and corporate logos. Already shown your class ambigrams? Feeling pressured to inject biology into your mathematics courses? Look no farther. My colleague sent me a link to the website…