induction x;simpl.
apply OrI1;simpl;apply ImpI;is_ass.
apply OrI2;apply IHx.
apply in_app_or in H0 as [].
apply in_split in H as (?&?&?);subst.
rewrite app_ass;apply (Clause_provable_2 (LPos x)).
inversion H;[discriminate|].
apply in_split in H0 as (?&?&?);subst.
apply (Clause_provable_2 (LNeg x)).
Qed.

Theorem CNF_provable : forall ll, Valid_CNF ll -> Provable (CNFtoPropF ll).
intros;induction ll;unfold CNFtoPropF;simpl.