Description: Formula-building rule for restricted existential quantifier (inference form). (Contributed by NM, 22-Oct-1999)
Ref | Expression | ||
---|---|---|---|
Hypothesis | reubii.1 | |- ( ph <-> ps ) |
|
Assertion | reubii | |- ( E! x e. A ph <-> E! x e. A ps ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | reubii.1 | |- ( ph <-> ps ) |
|
2 | 1 | a1i | |- ( x e. A -> ( ph <-> ps ) ) |
3 | 2 | reubiia | |- ( E! x e. A ph <-> E! x e. A ps ) |