Description: Obsolete version of trunorfal as of 17-Dec-2023. (Contributed by Remi, 25-Oct-2023) (Proof modification is discouraged.) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | trunorfalOLD | |- ( ( T. -\/ F. ) <-> F. ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | df-nor | |- ( ( T. -\/ F. ) <-> -. ( T. \/ F. ) ) |
|
| 2 | tru | |- T. |
|
| 3 | 2 | orci | |- ( T. \/ F. ) |
| 4 | 3 | notnoti | |- -. -. ( T. \/ F. ) |
| 5 | 4 | bifal | |- ( -. ( T. \/ F. ) <-> F. ) |
| 6 | 1 5 | bitri | |- ( ( T. -\/ F. ) <-> F. ) |