Description: Given a is equivalent to T., Given b is equivalent to F., there exists a proof for that a iff b is false. (Contributed by Jarvin Udandy, 7-Sep-2020)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | aifftbifffaibifff.1 | |- ( ph <-> T. ) | |
| aifftbifffaibifff.2 | |- ( ps <-> F. ) | ||
| Assertion | aifftbifffaibifff | |- ( ( ph <-> ps ) <-> F. ) | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | aifftbifffaibifff.1 | |- ( ph <-> T. ) | |
| 2 | aifftbifffaibifff.2 | |- ( ps <-> F. ) | |
| 3 | 1 | aistia | |- ph | 
| 4 | 2 | aisfina | |- -. ps | 
| 5 | 3 4 | abnotbtaxb | |- ( ph \/_ ps ) | 
| 6 | 5 | axorbtnotaiffb | |- -. ( ph <-> ps ) | 
| 7 | nbfal | |- ( -. ( ph <-> ps ) <-> ( ( ph <-> ps ) <-> F. ) ) | |
| 8 | 7 | biimpi | |- ( -. ( ph <-> ps ) -> ( ( ph <-> ps ) <-> F. ) ) | 
| 9 | 6 8 | ax-mp | |- ( ( ph <-> ps ) <-> F. ) |