theorem nfrapp {x: nat} (F: set x) (a: nat x):
$ FS/ x F $ >
$ FN/ x a $ >
$ FS/ x F @' a $;
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | hyp h2 | FN/ x a |
|
| 2 | nfnv | FN/ x a1 |
|
| 3 | 1, 2 | nfpr | FN/ x a, a1 |
| 4 | hyp h1 | FS/ x F |
|
| 5 | 3, 4 | nfel | F/ x a, a1 e. F |
| 6 | 5 | nfab | FS/ x {a1 | a, a1 e. F} |
| 7 | 6 | conv rapp | FS/ x F @' a |