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 ) |
| 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 ) |