theorem sbethh (a: nat) {x: nat} (p q: wff x):
$ F/ x q $ >
$ p $ >
$ x = a -> (p <-> q) $ >
$ q $;
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | hyp h | F/ x q |
|
| 2 | hyp e | x = a -> (p <-> q) |
|
| 3 | 1, 2 | sbeh | [a / x] p <-> q |
| 4 | hyp hp | p |
|
| 5 | 4 | sbth | [a / x] p |
| 6 | 3, 5 | mpbi | q |