reserve m, n for Nat;

theorem Th40:
  for n being non zero Nat holds NatDivisors n c= Seg n
proof
  let n be non zero Nat;
  let x be object;
  assume x in NatDivisors n;
  then consider k being Nat such that
A1: x = k and
A2: k <> 0 & k divides n;
  1 <= k & k <= n by A2,NAT_1:14,NAT_D:7;
  hence thesis by A1,FINSEQ_1:1;
end;
