Definition forces_t (k : kripke_tree) := forces_t2 k k.

Lemma forces_a_imp_b_imp_c__forces_a_imp_falsum_imp_c_t2 : forall (k k' : kripke_tree) (a b c : form), Suc k' k -> forces_t2 k k' (Imp (Imp a b) c) -> forces_t2 k k' (Imp (Imp a Falsum) c).