theorem Th6:
  for f,g being FinSequence holds f^^{g} = {f^g}
  proof
    let f,g be FinSequence;
    thus f^^{g} c= {f^g}
    proof
      let a; assume a in f^^{g};
      then consider p being Element of {g} such that
A2:   a = f^p & p in {g};
      p = g by TARSKI:def 1;
      hence thesis by A2,TARSKI:def 1;
    end;
    let a; assume a in {f^g};
    then a = f^g & g in {g} by TARSKI:def 1;
    hence thesis;
  end;
