reserve X for non empty CUNITSTR;
reserve a, b for Complex;
reserve x, y for Point of X;
reserve X for ComplexUnitarySpace;
reserve x, y, z, u, v for Point of X;

theorem Th39:
  0 <= ||.x.||
proof
  0 <= Re(x.|.x) by Def11;
  then 0 <= |.(x.|.x).| by Th29;
  hence thesis by SQUARE_1:def 2;
end;
