-4 6 setxrange
-1 5 setyrange

20 setxunit

/U {4 4} def
/u {-6 0} def
/V {0 0} def
/v {3 3} def
U u addv /U' defpoint
V v addv /V' defpoint

/A {3 2} def
/B {-2 1} def

quadrillage

[A B U V] points

U U' (->) line
V V' (->) line

setTimesItalic
   (A) A dltext
   (B) B dltext
<tex>
$\vec u$
</tex>
U U' milieu [1.2 dup] uctexlabel
<tex>
$\vec v$
</tex>
V V' milieu [1.2 dup] uctexlabel