usecolor
-2 2 setxrange
-2 3 setyrange

%% echelle
100 setxunit

%% position de la camera
3 10 6 SetCamPos
0 0 0 SetCamView

2 setlinejoin 

%% dessin de la sphere
/aretescachees false def
.5 setlinewidth         %% epaisseur du trait
.6 setgray              %% niveau de gris
2 [18 36] newsphere
drawsolid


%% r, theta, phi
/A {2 90 20} def
/B {2 60 40} def
/C {2 120 70} def

pointilles
.75 setlinewidth
bleu
A B arcspherique
orange
A C arcspherique
rouge
C B arcspherique

.5 setlinewidth
continu noir
[0 0 0 A rtp2xyz] ligne3d
[0 0 0 B rtp2xyz] ligne3d
[0 0 0 C rtp2xyz] ligne3d

%% on marque les points
orange
A rtp2xyz point3d
C rtp2xyz point3d
B rtp2xyz point3d
noir
0 0 0 point3d

%% et on inscrit leurs noms
18 setfontsize
setTimesItalic
   (A) A rtp2xyz uctext3d
   (B) B rtp2xyz cltext3d
   (C) C rtp2xyz urtext3d
   (O) 0 0 0 dltext3d