(b) -- Direction Field

> DOMAIN := t = 0 .. 1 ; # specify reasonable interval for indep var

> WINDOW := R = 0 .. 3,

> F = 0 .. 3 ; # specify reasonable intervals for all dependent vars

> DIRplot := DEplot( MODEL, VAR, DOMAIN, WINDOW, arrows = MEDIUM,

> title = `Direction Field for # 12?` ):

> DIRplot;

>