 Pythagoras discovered many of the properties of what would become trigonometric functions.The Pythagorean Theorem, p2 + b2 = h2 is a representation of the fundamental trigonometric identity sin2(x) + cos2(x) = 1.The length 1 is the hypotenuse of any right triangle, and has legs length sin(x) and cos(x) with x being one of the two non-right angles.