Description: A symmetry with <-> .
See negsym1 for more information. (Contributed by Anthony Hart, 4-Sep-2011)
Ref | Expression | ||
---|---|---|---|
Assertion | bisym1 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | nbfal | |
|
2 | 1 | bibi2i | |
3 | pm5.19 | |
|
4 | 3 | pm2.21i | |
5 | 2 4 | sylbir | |