theorem Th65:
  |.-z.| = |.z.|
proof
A1: -z = [*-Rea z, -Im1 z, -Im2 z, -Im3 z*] by Th55;
  then
A2: Rea -z = - Rea z by Th16;
A3: Im1 -z = - Im1 z by A1,Th16;
A4: Im2 -z = - Im2 z by A1,Th16;
  Im3 -z = - Im3 z by A1,Th16;
  hence thesis by A2,A3,A4;
end;
