End comp_ev_3.

(* Specifications: *)
Theorem composition_th4 :
forall (F G X : Ens) (f : is_a_function F) (g : is_a_function G)
(i : IN X (Domain F)) (j : IN (EV F X) (Domain G)),
EQ (EV (COMP F G) X) (EV G (EV F X)).