
theorem Th7:
  for X being set, F being SetSequence of X holds meet F c= lim_inf F
proof
  let X be set, F be SetSequence of X;
  let x be object;
  assume x in meet F;
  then for k being Nat holds x in F.(0 qua Nat+k) by Th3;
  hence thesis by Th4;
end;
