reserve a,b,c,d for Real;
reserve z,z1,z2 for Complex;

theorem
  |.z*z.| = |.z*z*'.|
proof
  thus |.z*z.| = |.z.|*|.z.| by Th65
    .= |.z.|*|.z*'.| by Th53
    .= |.z*z*'.| by Th65;
end;
