(********** Cartesian product *********)
Definition PowerPlus (A : Ens) := union A (Powerset A).

(* Specifications: *)
Theorem PowerPlus_th1 : forall A : Ens, SUB A (PowerPlus A).
Proof fun A : Ens => union_pr1 A (Powerset A).
Theorem PowerPlus_th2 : forall A : Ens, SUB (Powerset A) (PowerPlus A).
Proof fun A : Ens => union_pr2 A (Powerset A).