Thread Subject: Phase trajectory problem. Need some tips.

Hi.

For a couple of days I'm trying to solve the problem with my task.
I must write a script, which will draw a family of phase trajectory (x1 - x2) of nonlinear dynamic system described by differential equation:

x1' = x2
x2' = -(1/T)*x2 - (K/T)*sign(B - x1)

where: T, K, B are constant. Starting statements of state coordinates: x1(0) = x*10, x2(0) = x*20.

Which method should I use to solve that task? Van Der Pol equation, or ODE45 function?

Plese help me. I will be gratefull for every tip.

Cheers!