Description: Obsolete version of opeq2 as of 25-May-2024. (Contributed by NM, 25-Jun-1998) (Revised by Mario Carneiro, 26-Apr-2015) (Proof modification is discouraged.) (New usage is discouraged.)
Ref | Expression | ||
---|---|---|---|
Assertion | opeq2OLD |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eleq1 | ||
2 | 1 | anbi2d | |
3 | preq2 | ||
4 | 3 | preq2d | |
5 | 2 4 | ifbieq1d | |
6 | dfopif | ||
7 | dfopif | ||
8 | 5 6 7 | 3eqtr4g |