Description: Obsolete version of sb3 as of 21-Feb-2024. (Contributed by NM, 5-Aug-1993) (Proof modification is discouraged.) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | sb3OLD | |- ( -. A. x x = y -> ( E. x ( x = y /\ ph ) -> [ y / x ] ph ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | equs5 | |- ( -. A. x x = y -> ( E. x ( x = y /\ ph ) <-> A. x ( x = y -> ph ) ) ) |
|
| 2 | sb2 | |- ( A. x ( x = y -> ph ) -> [ y / x ] ph ) |
|
| 3 | 1 2 | syl6bi | |- ( -. A. x x = y -> ( E. x ( x = y /\ ph ) -> [ y / x ] ph ) ) |