Description: Given a, a implies it is not the case a implies a self contradiction. (Contributed by Jarvin Udandy, 7-Sep-2020)
| Ref | Expression | ||
|---|---|---|---|
| Hypothesis | ainaiaandna.1 | |- ph | |
| Assertion | ainaiaandna | |- ( ph -> -. ( ph -> ( ph /\ -. ph ) ) ) | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | ainaiaandna.1 | |- ph | |
| 2 | 1 | atnaiana | |- -. ( ph -> ( ph /\ -. ph ) ) | 
| 3 | 2 | a1i | |- ( ph -> -. ( ph -> ( ph /\ -. ph ) ) ) |