Description: Obsolete version of ifpn as of 5-May-2024. (Contributed by BJ, 30-Sep-2019) (Proof modification is discouraged.) (New usage is discouraged.)
Ref | Expression | ||
---|---|---|---|
Assertion | ifpnOLD | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | notnotb | |
|
2 | 1 | imbi1i | |
3 | 2 | anbi2ci | |
4 | dfifp2 | |
|
5 | dfifp2 | |
|
6 | 3 4 5 | 3bitr4i | |