Description: A proper class vanishes in an unordered pair. (Contributed by NM, 15-Jul-1993)
Ref | Expression | ||
---|---|---|---|
Assertion | prprc1 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | snprc | |
|
2 | uneq1 | |
|
3 | df-pr | |
|
4 | uncom | |
|
5 | un0 | |
|
6 | 4 5 | eqtr2i | |
7 | 2 3 6 | 3eqtr4g | |
8 | 1 7 | sylbi | |