-1 1 setxrange
-1 1 setyrange

/X {-0.7 0} def
/Y {0.7 0} def
/M {X Y milieu} def

/c {X Y diamcercle} def
75 c cpoint /C defpoint
225 c cpoint /A defpoint
315 c cpoint /B defpoint

[A B C] polygone
[M A] ligne
B A C 0.12 (-) tripointarc
C B A 0.12 (-) tripointarc
A C B 0.12 (-) tripointarc

[A B C M] points
0 3600 c Cercle 

(A) A [1.5 dup] dltext
(B) B [1.5 dup] drtext
(C) C [1.5 dup] uctext
(M) M [1.5 dup] uctext

<latex>
$a$
</latex>
0.5 0 [1.6 dup] ultexlabel

<latex>
$c$
</latex>
0.1 -0.62 [1.6 dup] ultexlabel

<latex>
$b$
</latex>
-0.15 0 [1.6 dup] ultexlabel

<latex>
$r$
</latex>
-0.1 -0.2 [1.6 dup] ultexlabel

<latex>
$\gamma$
</latex>
0.25 0.4 [1.6 dup] ultexlabel

<latex>
$\alpha$
</latex>
-0.4 -0.48 [1.6 dup] urtexlabel

<latex>
$\beta$
</latex>
0.28 -0.49 [1.6 dup] urtexlabel