@options;
  
@figure;
  A = point( -4 , 0.23 );
  B = point( 1.63 , 0.7 );
  sAB = segment( A , B );
  C = point( -2.07 , 5.7 );
  sBC = segment( B , C );
  sCA = segment( C , A );
  medsAB = mediatrice( sAB )  { orange };
  medsBC = mediatrice( sBC )  { orange };
  O = intersection( medsAB , medsBC )  { vertfonce };
  ceOA = cercle( O , A )  { vertfonce };
