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 Th22:
  for D being set, D1 being Subset of D for p being FinSequence of D1
  holds p is FinSequence of D
proof
  let D be set, D1 be Subset of D;
  let p be FinSequence of D1;
  rng p c= D1 by FINSEQ_1:def 4;
  hence rng p c= D by XBOOLE_1:1;
end;
