Capitolul 1 Ecuatii diferentiale de ordinul ˆıntâi rezolvabile prin ...

Metode numerice 153
care aratǎ cǎ, din orice punct ar pleca solut¸iile, toate vor evolua cǎtre
zero (Figura 28):
> with(DEtools):phaseportrait([D(x)(t)=y(t)-z(t),
D(y)(t)=z(t)-x(t),D(z)(t)=x(t)-y(t)*2],[x(t),y(t),z(t)],
t=-10..50,[[x(0)=3,y(0)=3,z(0)=3]],stepsize=.05,
scene=[z(t),y(t)],linecolour=sin(t*Pi/2),
method=classical[rk4]);
Figura 28