@options;

@figure;
  O = point( 0.64 , 0.09 );
  A = point( -6.47 , -1.37 );
  ceOA = cercle( O , A );
  B = pointsur( ceOA , 99.77 );
  C = symetrique( A , O );
  D = symetrique( B , O );
  sAC = segment( A , C );
  sAB = segment( A , B );
  sBC = segment( B , C );
  sCD = segment( C , D );
  sDA = segment( D , A );
  sDB = segment( D , B );

@analyse;
angle(ABC) = 90 degrés
angle(BCD) = 90 degrés
angle(CDA) = 90 degrés