Description: A composition is not affected by a double converse of its second argument. (Contributed by NM, 8-Oct-2007)
Ref | Expression | ||
---|---|---|---|
Assertion | cocnvcnv2 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | cnvcnv2 | ||
2 | 1 | coeq2i | |
3 | resco | ||
4 | relco | ||
5 | dfrel3 | ||
6 | 4 5 | mpbi | |
7 | 2 3 6 | 3eqtr2i |