Description: An equation between setvar is free of any other setvar. Usage of this theorem is discouraged because it depends on ax-13 . (Contributed by Wolf Lammen, 10-Jun-2019) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | nfeqf1 | |- ( -. A. x x = y -> F/ x y = z ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | nfeqf2 | |- ( -. A. x x = y -> F/ x z = y ) |
|
| 2 | equcom | |- ( z = y <-> y = z ) |
|
| 3 | 2 | nfbii | |- ( F/ x z = y <-> F/ x y = z ) |
| 4 | 1 3 | sylib | |- ( -. A. x x = y -> F/ x y = z ) |