The body is, for all intents and purposes, an extraordinarily complex machine. This requires a multitude of parts all working together in complicated relationships from the micro- to macromolecular ...

In this triangle \(a^2 = b^2 + c^2\) and angle \(A\) is a right angle. Pythagoras' theorem only works for right-angled triangles, so you can use it to test whether a triangle has a right angle or not.