@options;
  repereortho(220,170,30,1,1){ 0 , moyen , noir , num1 ,i};
@figure;
  O = point( -5.07 , -1.93 );
  S = point( 3.2 , -1.93 );
  demiOS = demidroite( O , S );
  perpOdemiOS = perpendiculaire( O , demiOS );
  M = pointsur( perpOdemiOS , 6.3 );
  A = pointsur( perpOdemiOS , 2.6 );
  cerayA6 = cerclerayon( A , 6 )  { i };
  C = intersection( demiOS , cerayA6 , 1 );
  sAC = segment( A , C );
  cerayA3 = cerclerayon( A , 3 )  { i };
  cediaAC = cercledia( A , C )  { i };
  B = intersection( cerayA3 , cediaAC , 1 )  { trace };
  sAB = segment( A , B );
  sBC = segment( B , C );
  I = milieu( sAC )  { trace };