Proposition 47 of Book 1 of Euclid's Elements, sometimes referred to as a verse of the gospel as Euclid 1.47, is commonly known as the Pythagorean theorem. After more than two millennia and about 400 different proofs, Euclid's remains a classic, still taught in secondary schools as an archetype of logical deduction. This Demonstration, designed for classroom use, combines Euclid's text with an animated version of his classical diagram.
Euclid's text is from Fitzpatrick's bilingual edition of the Elements , with minor variations by the author. Colors and graphic ideas are from Byrne's 1847 four-color edition .
 R. Fitzpatrick, ed., Euclid's Elements of Geometry: The Greek Text of J.L. Heiberg (1883–1885) from Euclidis Elementa, edidit et Latine Interpretatus est I. L. Heiberg, in Aedibus B. G. Teubneri, 1883–1885, 2008.
 O. Byrne, The Elements of Euclid, London: William Pickering, 1847.