User:Numiri/KinderCalculus/trig

To take the shortest path to Calculus, we don't need to cover all the trigonometric identities. We just need to   define the sin & cos function in terms of a right triangle  teach the unit circle coordinate values of simple angles:  0, pi/6, pi/4, pi/3, pi/2, ...  Basic sin & cos can form the rotation matrix, which will later lead to hyperbolic rotations of Special Relativity.