Description: Substitution does not change a distinctor. Usage of this theorem is discouraged because it depends on ax-13 . (Contributed by NM, 5-Aug-1993) (New usage is discouraged.)
Ref | Expression | ||
---|---|---|---|
Assertion | sbequ6 | |- ( [ w / z ] -. A. x x = y <-> -. A. x x = y ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | nfnae | |- F/ z -. A. x x = y |
|
2 | 1 | sbf | |- ( [ w / z ] -. A. x x = y <-> -. A. x x = y ) |