reserve n for Nat;

theorem Th50:
  for D be set for f,g be FinSequence of D holds (f^'g)|(len f) = f
proof
  let D be set;
  let f,g be FinSequence of D;
  f|len f = f|(Seg len f) by FINSEQ_1:def 16;
  hence thesis by Th49,FINSEQ_2:20;
end;
