theorem Th14:
   for A being Matrix of F_Real holds MXR2MXF MXF2MXR A = A
   proof
     let A be Matrix of F_Real;
     MXR2MXF MXF2MXR A = MXF2MXR A by MATRIXR1:def 1;
     hence thesis by MATRIXR1:def 2;
   end;
