Description: Obsolete version of nornot as of 8-Dec-2023. (Contributed by Remi, 25-Oct-2023) (Proof modification is discouraged.) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | nornotOLD | |- ( -. ph <-> ( ph -\/ ph ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | pm4.56 | |- ( ( -. ph /\ -. ph ) <-> -. ( ph \/ ph ) ) |
|
| 2 | pm4.24 | |- ( -. ph <-> ( -. ph /\ -. ph ) ) |
|
| 3 | df-nor | |- ( ( ph -\/ ph ) <-> -. ( ph \/ ph ) ) |
|
| 4 | 1 2 3 | 3bitr4i | |- ( -. ph <-> ( ph -\/ ph ) ) |