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

Lemma forces_a0_imp_c_and_a1_imp_c_and_c_imp_b__forces_a0_or_a1_imp_b_t : forall (k : kripke_tree) (a0 a1 c b : form), forces_t k (Imp a0 c) -> forces_t k (Imp a1 c) -> forces_t k (Imp c b) -> forces_t k (Imp (OrF a0 a1) b).