/widthangledroit 5 def

%% syntaxe : A B C angledroit --> dessine un angle droit en B
/angledroit {
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
   gsave
   newpath
      B stranslate
      thin setlinewidth
      B A A B alpha rotatepoint
      milieu angle
      rotate
      widthangledroit dup moveto
      widthangledroit dup neg rlineto
      widthangledroit neg dup rlineto
   stroke  
   grestore
end
} def