proposition: Theorem andb3_exchange : forall b c d, andb (andb b c) d = andb (andb b d) c.
proof: Proof. Admitted. Theorem andb_true_elim2 : forall b c : bool, andb b c = true -> c = true. Proof. intros b c. destruct b eqn:Eb. - simpl. intros H. rewrite H. reflexivity. - simpl. intros H. destruct c eqn:Ec. + reflexivity. + rewrite H. reflexivity. Qed.
imports: Coq(Arith List) LF(IndProp) Coq(Lia)