[font=Trebuchet MS][size=150][b]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][/b][/size][/font]