Mathematically, the problem is stated as follows. Let m 1 , 2 be the masses of the two massive bodies, with (planar) coordinates ( x 1 , y 1 ) and ( x 2 , y 2 ) , and let ( x , y ) be the coordinates of the planetoid. For simplicity, choose units such that the distance between the two massive bodies, as well as the gravitational constant, are both equal to 1 . Then, the motion of the planetoid is given by