The Pythagorean Theorem.

This is an animation of the first [i]Proof Without Words[/i] ever to appear in the Mathematical Association of America's [i]Mathematics Magazine[/i]. The official citation is Isaacs, Rufus, "Two Mathematical Papers without Words", [i]Mathematics Magazine[/i], Vol. 48, No. 4 (Sep., 1975), p. 198.
The Pythagorean Theorem.

Information: The Pythagorean Theorem.