Definition inE := ((in_set0, in_set1, in_setU, in_setI, in_setD), inE).Definition subset_trans B A C := (@le_trans _ _ B A C).Definition proper_trans B A C := (@lt_trans _ _ B A C).Definition sub_proper_trans B A C := (@le_lt_trans _ _ B A C).Definition proper_sub_trans B A C := (@lt_le_trans _ _ B A C).Definition proper_sub A B := (@ltW _ _ A B).

Lemma imsetS f A A' : A \subset A' -> imset f A \subset imset f A'.