Online geometry circle calculator to calculate epicycloid (the abscissa of a point) from user inputs.
x = ( R + r ) · cos θ - r · cos ( θ + a )
x = The abscissa of the point
R = Radius of the larger circle
r = Radius of the smaller circle
θ = Tthe radian from the starting point to the tangential point
a = The radian from the tangential point to the moving point