%% auteur : gh
70 setxunit
-2 3 setxrange
-1 3 setyrange

/cosa {pi 6 div Cos} def
/sina {pi 6 div Sin} def
/O {0 0} def
/A {cosa sina} def
/B {0 sina sub cosa} def
/M {2 cosa mul 2 sina mul} def
/Mx {2 cosa mul 0} def
/My {0 2 sina mul} def

tracerepere
16 setfontsize
setTimesItalic
   (O) O dltext

<tex> 
$$
\vec{\imath }
$$ 
</tex> 
0.5 0  [1.5 1.5] dctexlabel 

<tex> 
$$
\vec{\jmath }
$$ 
</tex> 
0 0.5  [1.5 1.5] cltexlabel 

bleu
pointilles
M Mx (-) line
M My (-) line
O M (-) line
[M] points

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

<tex> 
$$
\vec{u}_\theta
$$ 
</tex> 
cosa 2 div sina 2 div  [1.5 1.5] {30} uctexlabel 

<tex> 
$$
\vec{v}_\theta
$$ 
</tex> 
0 sina 2 div sub cosa 2 div [1.5 1.5]{30} cltexlabel 

setTimesItalic
   (M) M ultext
setSymbol
   (q) .5 .12 cctext
%   (r) A {30} uctext
/arrowangle -5 store
1 0 O A 0.4 (->) tripointarc