[font=Trebuchet MS][b][size=150]If the smaller circle has radius r, and the larger circle has radius R,[br][color=#ff7700][br]x = (R+r)*cos(theta) - d*cos((R+r)/r*theta)[br][br]y = (R+r)*sin(theta) - d*sin((R+r)/r*theta)[/color][/size][/b][/font]