Date: Sat, 23 Nov 1996 12:44:00 -0500

From: Alex Bogomolny

Dear DJ13181:

Your question caused me to look around through my library and search the Internet. A little of what I discovered made for a content of a paragraph I added as a Remark to my Pythagorean page.

"The statement of the Theorem was discovered on a Babylonean tablet circa 1900-1600 B.C. Whether Pythagoras (c.560-c.480 B.C.) or any one from his School was the first to discover its proof can't be claimed with any degree of credibility. Euclid's (c 300 B.C.) Elements furnish the first and, later, the standard reference in Geometry. Jim Morey's applet follows the Proposition I.47 (First Book, Proposition 47), mine VI.31. The Theorem is reversible (I.48) which means that a triangle whose sides satisfy a^2+b^2=c^2 is right angled."

In every source, if you enjoy this kind of browsing when one absorbes facts and information one was not deliberately looking for, there could be something interesting to learn.

cites 10 proof of the Theorem and references to the American Math Monthly ~1890.David Eppstein in The Geometry Junkyard mentions the book

D. Wells, *The Penguin Dictionary of Curious and Interesting Geometry*,
Penguin, 1991.

which, in turn, cites a book from 1940 with 367 different proofs of the Theorem.

Regards and good luck in your search.