theorem abeqd (G: wff) {x: nat} (p q: wff x): $ G -> (p <-> q) $ > $ G -> {x | p} == {x | q} $;
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | abeq | A. x (p <-> q) -> {x | p} == {x | q} |
|
2 | hyp h | G -> (p <-> q) |
|
3 | 2 | iald | G -> A. x (p <-> q) |
4 | 1, 3 | syl | G -> {x | p} == {x | q} |