Description: Modus tollens inference. (Contributed by NM, 5-Jul-1994) (Proof shortened by Wolf Lammen, 15-Sep-2012)
Ref | Expression | ||
---|---|---|---|
Hypotheses | mtoi.1 | |
|
mtoi.2 | |
||
Assertion | mtoi | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | mtoi.1 | |
|
2 | mtoi.2 | |
|
3 | 1 | a1i | |
4 | 3 2 | mtod | |