This is an inofficial mirror of http://metamath.tirix.org for personal testing of a visualizer extension only.
Metamath Proof Explorer
Description: A contraposition inference. (Contributed by NM, 12-Mar-1993)
|
|
Ref |
Expression |
|
Hypothesis |
con2bii.1 |
|- ( ph <-> -. ps ) |
|
Assertion |
con2bii |
|- ( ps <-> -. ph ) |
Proof
| Step |
Hyp |
Ref |
Expression |
| 1 |
|
con2bii.1 |
|- ( ph <-> -. ps ) |
| 2 |
|
notnotb |
|- ( ps <-> -. -. ps ) |
| 3 |
2 1
|
xchbinxr |
|- ( ps <-> -. ph ) |