reserve X for non empty set;

theorem Th6:
  for ET being U_FMT_filter non empty strict FMT_Space_Str,
  x being Element of ET holds the carrier of ET in U_FMT x
  proof
    let ET be U_FMT_filter non empty strict FMT_Space_Str,
    x be Element of ET;
    U_FMT x is Filter of the carrier of ET by Def2;
    hence thesis by CARD_FIL:5;
  end;
