The Pythagorean theorem is one of the most famous theorems of geometry. It is often attributed to Pythagoras of Samos (Greece), who lived in the sixth century B.C. The theorem states that in any right triangle, the square of the hypotenuse of the triangle (the side opposite the right angle) is equal to the sum of the squares of the other two sides, or c 2 = a 2 + b 2 .
This theorem was probably known long before the time of Pythagoras; it is thought to have been used by the ancient Egyptians and Babylonians. Nevertheless, Pythagoras (or some member of his school) is credited with the first proof of the theorem.
The converse of the Pythagorean theorem is also true. That is, if a triangle with sides a, b, and c has c 2 = a 2 + b 2 , we know that the triangle is a right triangle.