reserve i,j,k,n for Nat;
reserve D for non empty set,
  p for Element of D,
  f,g for FinSequence of D;

theorem Th28:
  for f being FinSequence holds f/^0 = f
proof
  let f be FinSequence;
A1: 0 <= len f;
A2: now
    let i be Nat;
    assume 1 <= i & i <= len(f/^0);
    then i in dom(f/^0) by FINSEQ_3:25;
    hence (f/^0).i = f.(i+0) by A1,RFINSEQ:def 1
      .= f.i;
  end;
  len(f/^0) = len f - 0 by RFINSEQ:def 1;
  hence thesis by A2;
end;
