(b) -- Direction Field
> DOMAIN := t = 0 .. 1 ; # specify reasonable interval for indep var
> WINDOW := x = -2 .. 2,
> y = -2 .. 2 ; # specify reasonable intervals for all dependent vars
> DIRplot := DEplot( MODEL, VAR, DOMAIN, WINDOW, arrows = MEDIUM,
> title = `Direction Field for # 16` ):
> DIRplot;
>