-3.5 4.5 setxrange
-3.5 4.5 setyrange

12 setxunit

/A {-3 -3} def
/B {-3 3} def
/C {3.5 -3} def

gsave
bleu
B C A 1 (-) tripointarc
A B C .75 (=) tripointarc
C A B angledroit
grestore


1.25 setcurvelinewidth
[A B C] polygone