Description: A contraposition inference. (Contributed by NM, 12-Mar-1993) (Proof shortened by Wolf Lammen, 13-Oct-2012)
Ref | Expression | ||
---|---|---|---|
Hypothesis | con1bii.1 | |
|
Assertion | con1bii | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | con1bii.1 | |
|
2 | notnotb | |
|
3 | 2 1 | xchbinx | |
4 | 3 | bicomi | |