Hint Resolve closed_wrt_not1 : closed.

Lemma closed_wrt_tc_andp:
forall {cs: compspecs} S a b,
closed_wrt_vars S (denote_tc_assert a) ->
closed_wrt_vars S (denote_tc_assert b) ->
closed_wrt_vars S (denote_tc_assert (tc_andp a b)).