Description: Replace ax-10 in nfa1 with a substitution hypothesis. (Contributed by SN, 2-Sep-2025)
| Ref | Expression | ||
|---|---|---|---|
| Hypothesis | nfa1w.x | |- ( x = y -> ( ph <-> ps ) ) | |
| Assertion | nfa1w | |- F/ x A. x ph | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | nfa1w.x | |- ( x = y -> ( ph <-> ps ) ) | |
| 2 | 1 | cbvalvw | |- ( A. x ph <-> A. y ps ) | 
| 3 | nfv | |- F/ x A. y ps | |
| 4 | 2 3 | nfxfr | |- F/ x A. x ph |