
theorem Th27:
  for z, w be G_RAT holds g_rat_add.(z,w) = z+w
  proof
    let z, w be G_RAT;
    z in G_RAT_SET & w in G_RAT_SET;
    hence g_rat_add.(z,w) = addcomplex.(z,w) by FUNCT_1:49,ZFMISC_1:87
    .= z+w by BINOP_2:def 3;
  end;
