theorem notan2 (a b: wff): $ ~(a /\ b) <-> a -> ~b $;
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | bicom | (a -> ~b <-> ~(a /\ b)) -> (~(a /\ b) <-> a -> ~b) |
|
| 2 | notnot | a -> ~b <-> ~~(a -> ~b) |
|
| 3 | 2 | conv an | a -> ~b <-> ~(a /\ b) |
| 4 | 1, 3 | ax_mp | ~(a /\ b) <-> a -> ~b |