Metamath Proof Explorer


Theorem nfriota1

Description: The abstraction variable in a restricted iota descriptor isn't free. (Contributed by NM, 12-Oct-2011) (Revised by Mario Carneiro, 15-Oct-2016)

Ref Expression
Assertion nfriota1
|- F/_ x ( iota_ x e. A ph )

Proof

Step Hyp Ref Expression
1 df-riota
 |-  ( iota_ x e. A ph ) = ( iota x ( x e. A /\ ph ) )
2 nfiota1
 |-  F/_ x ( iota x ( x e. A /\ ph ) )
3 1 2 nfcxfr
 |-  F/_ x ( iota_ x e. A ph )