theorem Th60:
  0 <= |.z.|
proof
A1: 0 <= (Rea z)^2 by XREAL_1:63;
A2: 0 <= (Im1 z)^2 by XREAL_1:63;
A3: 0 <= (Im2 z)^2 by XREAL_1:63;
  0 <= (Im3 z)^2 by XREAL_1:63;
  hence thesis by A1,A2,A3,SQUARE_1:def 2;
end;
