Description: Obsolete version of nfiu1 as of 14-May-2025. (Contributed by NM, 12-Oct-2003) (Proof modification is discouraged.) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | nfiu1OLD | |- F/_ x U_ x e. A B |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | df-iun | |- U_ x e. A B = { y | E. x e. A y e. B } |
|
| 2 | nfre1 | |- F/ x E. x e. A y e. B |
|
| 3 | 2 | nfab | |- F/_ x { y | E. x e. A y e. B } |
| 4 | 1 3 | nfcxfr | |- F/_ x U_ x e. A B |