autocrop
20 setxunit

/A {0 0} def
/cerc1 {A 3} def
/cerc2 {A 5} def

/F {-100 cerc1 cpoint} def
/E {-140 cerc1 cpoint} def
/B {-20 cerc2 cpoint} def
/C {20 cerc2 cpoint} def

.9 setlinewidth
[A E B] polygone
.7 setlinewidth
.5 setgray
[A F C] polygone
noir

.5 setlinewidth
E A F .8 (-) tripointarc
B A C .8 (-) tripointarc
F A B .8 (=) tripointarc

setTimesItalic
   (A) A ultext
   (B) B drtext
   (C) C urtext
   (E) E dltext
   (F) F drtext
8 setfontsize
setSymbol
   (a) 0 A 1.1 cpoint cctext
   (a) -120 A 1.1 cpoint cctext
   (b) -60 A 1.1 cpoint cctext