reserve i,j,k,l for natural Number;
reserve A for set, a,b,x,x1,x2,x3 for object;
reserve D,D9,E for non empty set;
reserve d,d1,d2,d3 for Element of D;
reserve d9,d19,d29,d39 for Element of D9;
reserve p,q,r for FinSequence;

theorem Th46:
  for k being natural Number holds id Seg k is FinSequence of NAT
proof
  let k be natural Number;
  set I = id Seg k;
  reconsider k as Element of NAT by ORDINAL1:def 12;
  dom I = Seg k;
  then rng I = Seg k & I is FinSequence by FINSEQ_1:def 2;
  hence thesis by FINSEQ_1:def 4;
end;
