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Math Monday: Business Cards II


Imagine a regular tetrahedron. Mark the midpoint of one edge and draw straight lines to the vertices opposite that edge on the two faces incident to that edge. In your mental image, transmogrify that edge and those two lines into zippers and unzip them. What do you get? Believe it... Read more »

Math Monday: Even Greater Circle


For the Museum of Mathematics I have been remiss. I wrote an entire column on arrangements of great circles without once mentioning Buckminster Fuller. His original designs for domes involved bracing them solely with arcs of great circles. Since, on the surface of a sphere a great circle is the... Read more »