
theorem Th5:
  for f being FinSequence, k2 being Nat holds smid(f,1,k2)=f|k2
proof
  let f be FinSequence, k2 be Nat;
  thus smid(f,1,k2) = (f/^0)|(k2+1-'1) by NAT_2:8
    .= f|(k2+1-'1) by FINSEQ_5:28
    .=f|k2 by NAT_D:34;
end;
