EpicycloidFormed as the locus of a point on a circle (radius r1) rotated (without slipping) on the outside of a fixed circle (radius r2) then x = (r2 + r1) cos(theta)  r1 cos((r2 + r1) theta / r1)y = (r2 + r1) sin(theta)  r1 sin((r2 + r1) theta / r1)
