Proof
fun (R Y : Ens) (i : IN Y (Range R)) => inverse_EV_pr R Y (Range_pr2 R Y i).
Section Range_th1_proof.
Variable R : Ens.
Variable X Y : Ens.
Hypothesis i : IN (PAIR X Y) R.
Let step1 : Range_prop R Y.
Proof EXISTS_th1 (fun X1 : Ens => IN (PAIR X1 Y) R) X i.

(* Specifications: *)
Lemma Range_th1_Out : IN Y (Range R).
Proof Range_pr1 R Y step1.