%% auteur : gh
100 setxunit
-1 4 setxrange
-2 1 setyrange

/cosa {pi 6 div Cos} def
/sina {pi 6 div Sin} def
/O {0 0} def
/A {cosa sina} def
/B {3 0} def
/Ax {cosa 0} def
/Ay {0 sina} def
/OAA {0 -1.05} def
/OBB {0 -0.95} def
/AA {cosa -1.05} def
/BB {3 -0.95} def

1 setlinewidth
continu
O A (->) line
O B (->) line

<tex> 
$$
\vec{u}
$$ 
</tex> 
2.5 0  [1.5 1.5] dctexlabel 

<tex> 
$$
\vec{u}\,'
$$ 
</tex> 
cosa .8 mul sina .8 mul [1.5 1.5] ultexlabel 

bleu
pointilles
A Ax (-) line

2 setlinewidth
continu
O Ax (->) line

<tex> 
$$
p(\vec{u}\,')
$$ 
</tex> 
0.5 0 [1.5 1.5] dctexlabel 

noir
continu
0.5 setlinewidth
0 -1 2 -1 droite

2 setlinewidth
bleu
OAA AA (->) line
OBB BB (->) line

noir
<tex> 
Mesures alg\'ebriques 
de $\vec{u}$ et du projet\'e orthogonal de $\vec{u}\,'$
</tex> 
1.5 -1.5 [1.5 1.5] cctexlabel