Theorem prtlem80

Description: Lemma for prter2 . (Contributed by Rodolfo Medina, 17-Oct-2010)

	Ref	Expression
Assertion	prtlem80	|- ( A e. B -> -. A e. ( C \ { A } ) )

Proof

Step	Hyp	Ref	Expression
1		neldifsnd	|- ( A e. B -> -. A e. ( C \ { A } ) )