%@DATE: 30 mai 2005
 
 input fichierps;
 
 InitFichierPS(-200,-120,200,180);
 u = 0.85cm;
 
 % Le points fixe.
 pair A;
 A = (0,4u);
 
 % Le cercle.
 path cA;
 cA = fullcircle scaled 4u shifted A;
 
 % Les articulations.
 pair D,B,C,F,G,E;
 
 % Longueur des tiges qui s'appuient sur la droite.
 l := 6.5u;
 
 % Position des articulationssur les tiges (facteur).
 f := 0.8;
 
 vardef Point(expr p) =
     draw p withpen pencircle scaled 4;
     draw p withpen pencircle scaled 3 withcolor white;
 enddef;
 
 % L'ellipse;
 path e;
 
 
 for i=0 upto 90:
   beginfig(i+1);
     
     D := point (8*i/90) of cA;
     x := xpart D; y := ypart D;
     k := y/l;
     B := (x-l*sqrt(1-k*k),0);
     C := 2[B,(x,0)];
     F := f[D,B];
     G := f[D,C];
     E := 2[D,.5[F,G]];    
 
     fill cA withcolor 0.8white;
          
     drawoptions(withcolor 0.6white);    
     draw cA;
     draw (-1.3l,0)--(1.3l,0);
     drawoptions();
 
     drawarrow subpath (0,8*i/90) of cA;
     
     if i=0: 
 	e := E;
     else:
 	e := e -- E;
 	draw e withpen pencircle scaled 1 withcolor blue;
     fi
         
     drawoptions(withpen pensquare scaled 2 withcolor (1,0.08,0.58));	
     draw A--D;
     draw D--B;
     draw D--C;
     draw F--E;
     draw G--E;
     drawoptions();
 	
     Point(A);
     Point(B);
     Point(C);
     Point(D);
     Point(E); 
     Point(F);
     Point(G);   
 
   endfig;
 endfor;
 
 end