intros v A;induction A;try destruct IHA;try destruct IHA1;try destruct IHA2;split;simpl in *;
try trivial;try rewrite H;try rewrite H0;try rewrite H1;try rewrite H2;try trivial;
repeat rewrite orb_false_r;repeat rewrite orb_false_l;
try rewrite negb_andb;try rewrite negb_orb;try rewrite negb_involutive;reflexivity.
Qed.
(** Proof that NNF A is valid iff CNF A is valid*)

Lemma CNF_and_valid : forall v ll1 ll2, TrueQ v (CNFtoPropF (ll1 ++ ll2)) =
TrueQ v (CNFtoPropF ll1) && TrueQ v (CNFtoPropF ll2).