-6 6 setxrange
-2 6 setyrange

quadrillage

.7 setlinewidth
tracerepere

/f {1 exch div} def
/A {2 3 sqrt sub dup f} def
/B {2 3 sqrt add dup f} def

1.2 setlinewidth
1 ymax div xmax (f) Courbe
xmin 1 ymin div (f) Courbe
(neg 4 add) courbe

<tex>
$\vec \imath $
</tex>
.4 -.1 [1.5 dup] dctexlabel

<tex>
$\vec \jmath $ 
</tex>
-.1 .2 [1.5 dup] ultexlabel

<tex>
$\cal D$ 
</tex>
-2 5 [1.2 dup] urtexlabel

<tex>
$\cal H$ 
</tex>
-5 -.8 [1.2 dup] urtexlabel

[A B] dashpoints

setTimesItalic
   (x) xmax 0 (-10 0) dltext
   (y) 0 ymax  (0 -10) dltext
   (A) A urtext
   (B) B urtext