What shape does pythagorean apply to?

Answer 1

It's to do with The Greek mathematician called Pythagoras. He was into trangles, particulary right angles ones, where he came up with a theory that relates the lengths of each side in a right angle triangle.

Answer 2

The Pythagorean theorem applies to right-angled triangles. It states that the square of the length of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the other two sides.