Pythagoras was an ancient Greek mathematician and philosopher who is best known for the Pythagorean theorem, which states that in a right-angled triangle, the square of the length of the hypotenuse is equal to the sum of the squares of the lengths of the other two sides. He founded a religious and philosophical movement that influenced the development of Western mathematics and philosophy. Pythagoras is also credited with discovering the mathematical relationships of musical intervals, and his teachings had a profound impact on the development of Western thought.