It was then notated that if triangle ABC is a right triangle, with a right angle at C, then c2 = a2 + b2. Earlier, the converse of this theorem appears to have been used. This became proposition number 47 from Book I of Euclid's Elements ("Pythagorean," 2007).

Although this theorem is traditionally associated with Pythagoras, it is actually much older.

More than a millennium before the birth of Pythagoras, four Babylonian tablets were created demonstrating some knowledge of this theorem, circa 1900-1600 B.C.. At the very least, these works represent the knowledge of at least special integers known as Pythagorean triples that satisfy it.

In addition, the Rhind papyrus, created around 1650 B.C., shows that Egyptians had knowledge of the theorem as well. However, the first proof of this theorem is still credited to Pythagoras, despite the fact that some scholars believe it was independently discovered in several different...
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