Direction Field
> DOMAIN := t = 0 .. 2 ; # specify reasonable interval for indep vars
> WINDOW := x = 0 .. 10,
> y = -1 .. 0 ; # specify reasonable intervals for all dependent vars
>
> DIRplot := DEplot( MODEL, VAR, DOMAIN, WINDOW, arrows = MEDIUM,
> title = `Direction Field for #12(b)` ):
> DIRplot;
>