reserve z1,z2,z3,z4,z for Quaternion;

theorem Th32:
  |.z*z.| = |.z*'* z*'.|
proof
  |.z*'* z*'.|=|.z*'.|*|.z*'.| by QUATERNI:87
    .=|.z.|*|.z*'.| by QUATERNI:73
    .=|.z.|*|.z.| by QUATERNI:73;
  hence thesis by QUATERNI:87;
end;
