-5 5 setxrange
-5 5 setyrange
20 setxunit
quadrillage
tracerepere

/A {2 3 sqrt mul 2} def
/B {-2 3 sqrt mul -2} def
/C {0 -4} def
/G {C .3 mulv} def
2 2 setmkstep
marks
O 4 cercle
A C B angledroit

[A B C G] {times2} plot

1.2 setlinewidth
[A B C] polygone

setTimesItalic
   (O) O ultext
   (A) A urtext
   (B) B dltext
   (C) C drtext
   (G) G drtext