Description: A commutation rule for distinct variable specifiers. Usage of this theorem is discouraged because it depends on ax-13 . (Contributed by NM, 2-Jan-2002) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Hypothesis | naecoms.1 | |- ( -. A. x x = y -> ph ) |
|
| Assertion | naecoms | |- ( -. A. y y = x -> ph ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | naecoms.1 | |- ( -. A. x x = y -> ph ) |
|
| 2 | aecom | |- ( A. x x = y <-> A. y y = x ) |
|
| 3 | 2 1 | sylnbir | |- ( -. A. y y = x -> ph ) |