hi

I need to plot the phase portrait of a hamiltonian of 4-dimensional phase-space, and I have an adiabatic invariant, i.e. one of the momenta is conserverd. 

I don't know how to replace a constant for the conserved momentum and plot the 2-dimensional phase space.

I am writiing 

sys := {diff(Y1(t), t) = -(diff(K, y1)), diff(Y2(t), t) = -(diff(K, y2)), diff(y1(t), t) = diff(K, Y1), diff(y2(t), t) = diff(K, Y2)}

and using the DEplot tool as