The Bactra Review Geometry Civilized
In these proofs, one re-arranges the areas defined in the initial construction,
duplicating as needed, until the desired result is manifest. (This makes it
for a very slick proof of the Pythagorean theorem: see Geometry
Civilized, 4.2.) This technique would seem to be the origin of the
Chinese game called ``tangrams'' in the
west, but Heilbron (remarkably enough) misses the connection.