Source
``````%% gh
%% condition de cocyclicité

%% échelle et étendue de l'image
240 setxunit
-1.2 1.2 setxrange
-1.2 1.2 setyrange

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% définitions des couleurs
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

/coul0 {0 0 0 0.5 setcmykcolor} def %gris
/coul1 {noir} def
/coul2 {orange} def
/coul3 {rouge} def
/coul4 {bleu} def

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% le cercle
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

coul1
0 0 1 cercle

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% les points
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
coul3

/A {3 sqrt 2 div neg .5} def
A point
<latex>
\$A\$
</latex>
A [2.5 dup] ultexlabel

/B {0 1} def
B point
<latex>
\$B\$
</latex>
B [2.5 dup] urtexlabel

/C {0 1 neg} def
C point
<latex>
\$C\$
</latex>
C [2.5 dup] dctexlabel

/D {1 0} def
D point
<latex>
\$D\$
</latex>
D [2.5 dup] crtexlabel

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% les vecteurs
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/arrowscale {2.5 dup} def
[A C] (-) ligne
[A D] (-) ligne
[B C] (-) ligne
[B D] (-) ligne
C A D .2 (=) tripointarc
C B D .2 (=) tripointarc``````