theorem Th34:
  Rea(-z) = -(Rea z) & Im1(-z) = -(Im1 z) & Im2(-z) = -(Im2 z) &
  Im3(-z) = -(Im3 z)
proof
  -z = -Rea z + (-Im1 z)*<i> + (-Im2 z)*<j> + (-Im3 z)*<k> by Lm24; then
  -z = [*-Rea z,-Im1 z,-Im2 z,-Im3 z*] by Lm19;
  hence thesis by Th16;
end;
