Description: Given a implies b, not b, there exists a proof for a is F. (Contributed by Jarvin Udandy, 1-Sep-2016)
Ref | Expression | ||
---|---|---|---|
Hypotheses | aibnbaif.1 | ||
aibnbaif.2 | |||
Assertion | aibnbaif |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | aibnbaif.1 | ||
2 | aibnbaif.2 | ||
3 | 1 2 | aibnbna | |
4 | 3 | bifal |