//mediatrice d'un segment
  1;
  A:=point(-1.0-2.0*i);
  B:=point(2.0+3.0*i);
  segment(A,B);
  C1:=cercle(A,B-A);
  C2:=cercle(B,A-B);
  D:=droite(inter(C1,C2));
  M:=inter(segment(A,B),D);