%% syntaxe : A B C bissectrice --> B E ou E est un point de la bissectrice
/bissectrice {
10 dict begin
   /yC exch def
   /xC exch def
   /yB exch def
   /xB exch def
   /yA exch def
   /xA exch def
   /A {xA yA} def
   /B {xB yB} def
   /C {xC yC} def
   /alpha {A B C tripointangle} def
   B
   A B alpha rotatepoint
   A milieu
end
} def