theorem
  Rea (z*') = Rea z & Im1 (z*') = -Im1 z &
  Im2 (z*') = -Im2 z & Im3 (z*') = -Im3 z
proof
  z*' = [*Rea z, -Im1 z, -Im2 z, -Im3 z*] by Lm19;
  hence thesis by Th16;
end;
