Description: Obsolete as of 30-Jul-2023. Use sb6 instead. Version of sb2 with a disjoint variable condition, which does not require ax-13 . (Contributed by BJ, 31-May-2019) Revise df-sb . (Revised by Steven Nguyen, 8-Jul-2023) (Proof modification is discouraged.) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | sb2vOLD | |- ( A. x ( x = y -> ph ) -> [ y / x ] ph ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | sb6 | |- ( [ y / x ] ph <-> A. x ( x = y -> ph ) ) |
|
| 2 | 1 | biimpri | |- ( A. x ( x = y -> ph ) -> [ y / x ] ph ) |