solve system of nonlinear differential equations




diff(x,t,2) = f1(diff(x,t),diff(y,t));

diff(y,t,2) = f2(diff(x,t),diff(y,t));


initial conditions at t=0:

x:Xo;? y:Yo;? diff(x,t):Vxo;? diff(y,t): Vyo;


Please, What is the most expedient method for solving the above system of differential equations using Maxima?