-4 4 setxrange
-1 5 setyrange

.5 .5 setquadrillagestep
35 setxunit
/A {-1.5 0} def

/U {-3 1} def
/u {1 1.5} def
/V {0 3} def
/v {1.5 0} def
/W {0 2} def
/w {-1 -1} def
U u addv /U' defpoint
V v addv /V' defpoint
W w addv /W' defpoint

quadrillage

[A] points

setTimesItalic
   (A) A dltext

1.5 setlinewidth

[U V W] points
U U' (->) line
V V' (->) line
W W' (->) line
<tex>
$\vec u$
</tex>
U U' milieu [1.2 dup] ultexlabel
<tex>
$\vec v$
</tex>
V V' milieu [1.2 dup] uctexlabel
<tex>
$\vec w$
</tex>
W W' milieu [1.2 dup] ultexlabel