-1 6 setyrange
-4 4 setxrange

/a 3 def
/x 1 3 div def

/B {a neg 0} def
/C {a 0} def
/A {C B 60 rotatepoint} def

/P {x A B ABpoint} def
/M {x B C ABpoint} def
/N {x C A ABpoint} def

%%[A B C P M N] points

[P M N] polygone
1.5 setlinewidth
[A B C] polygone

A P 1 marked
B M 1 marked
N C 1 marked

setTimesItalic
    (A) A utext
    (B) B dltext
    (C) C drtext
    (P) P ultext
    (M) M dtext
    (N) N utext