theorem Th34:
  for M being FinSequence of D* holds M.i is FinSequence of D
proof
  let M be FinSequence of D*;
  per cases;
  suppose
    not i in dom M;
    then M.i = <*>D by FUNCT_1:def 2;
    hence thesis;
  end;
  suppose
A1: i in dom M;
A2: rng M c= D* by FINSEQ_1:def 4;
    M.i in rng M by A1,FUNCT_1:def 3;
    hence thesis by A2,FINSEQ_1:def 11;
  end;
end;
