Hi everyone!

I have an urgent problem!  I am dealing with an autonomous system of 2 differential equations.

First of all I have to plot  the phase plane (x,y) but I'd like to include a constraint (x^2+y^2<1 )in my system and I don't know how to do that!

what I've done by now:

>dfieldplot([diff(x(N),N)=-3*x(N)+sqrt(6)*(y(N))^2+3/2*x(N)*((x(N))^2+1-(y(N))^2), diff(y(N),N)=-sqrt(6)*x(N)*y(N)+3/2*y(N)*((x(N))^2+1-(y(N))^2)],
 [x(N),y(N)],N=0..20, x=-1..1, y=0..1, color=black, dirfield=[30,30]);