Proof
fun (F G X : Ens) (c : Comp_prop F G X) =>
Domain_th1 F (PR1 X) (Comp_INTER F G X) (Comp_INTER_th1 F G X c).

(* Specifications: *)
Theorem Comp_prop_th2 :
forall (F G X : Ens) (c : Comp_prop F G X), IN (PR2 X) (Range G).