Definition andRel (n : nat) (R S : naryRel n) : naryRel n.
intros.
induction n as [| n Hrecn].
exact (R && S).
simpl in |- *.
intros.
apply Hrecn.
apply (R H).
apply (S H).
Defined.

Lemma andRelPR :
forall (n : nat) (R R' : naryRel n),
isPRrel n R -> isPRrel n R' -> isPRrel n (andRel n R R').