Theorem nfiota1

Description: Bound-variable hypothesis builder for the iota class. (Contributed by Andrew Salmon, 11-Jul-2011) (Revised by Mario Carneiro, 15-Oct-2016)

	Ref	Expression
Assertion	nfiota1	|- F/_ x ( iota x ph )

Proof

Step	Hyp	Ref	Expression
1		dfiota2	|- ( iota x ph ) = U. { y | A. x ( ph <-> x = y ) }
2		nfaba1	|- F/_ x { y | A. x ( ph <-> x = y ) }
3	2	nfuni	|- F/_ x U. { y | A. x ( ph <-> x = y ) }
4	1 3	nfcxfr	|- F/_ x ( iota x ph )