theorem Th44:
  for f being Function of X,TOP-REAL n, g being Function of X,R^1 holds
  f<->g is Function of X,TOP-REAL n
  proof
    let f be Function of X,TOP-REAL n, g be Function of X,R^1;
    set h = f<->g;
A1: dom f = X by FUNCT_2:def 1;
 dom g = X by FUNCT_2:def 1;
then A2: dom h = X by A1,VALUED_2:61;
    for x st x in X holds h.x in the carrier of TOP-REAL n
    proof
      let x;
      assume
A3:   x in X;
      then reconsider X as non empty set;
      reconsider x as Element of X by A3;
      reconsider f as Function of X,TOP-REAL n;
      h.x = f.x-g.x by A2,VALUED_2:62;
      hence thesis;
    end;
    hence thesis by A2,FUNCT_2:3;
  end;
