In 2006, Art Stoner sent me the following model that illustrates the remarkable 4-piece dissection of an equilateral triangle to a square first described by Henry Dudeney in the Weekly Dispatch in 1902. The model is laser-cut out of 1/4" white plexiglas, with the square being 5 inches on a side. The pieces are out of a nice thick material, are a great size, and are very accurately cut.
Art is a mathematics educator who manufactures high-quality math instructional tools for high school teachers. He travels around the country to a variety of meetings for high school teachers, where he demonstrates and sells his tools. Take a look at Art's website: A+ Compass
UPDATE!: As of the summer of 2007, Art has improved the model so that it is now in translucent blue. See Haberdasher Set. Very attractive!
Photos copyright 2006-2007, Greg N. Frederickson.
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Dissections: Plane & Fancy
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Last updated August 10, 2007.