>>778
>d^2x/d^2t = (g/r^2)*xy - (a/r^2)*y^2
>d^2y/d^2t = (a/r^2)*xy - (g/r^2)*x^2

d^2x/dt^2 = (g/r^2)*xy - (a/r^2)*y^2
d^2y/dt^2 = (a/r^2)*xy - (g/r^2)*x^2
だろ。