Description: Membership in universal class of ordered pairs. (Contributed by NM, 4-Jul-1994)
Ref | Expression | ||
---|---|---|---|
Assertion | elvv | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | elxp | |
|
2 | vex | |
|
3 | vex | |
|
4 | 2 3 | pm3.2i | |
5 | 4 | biantru | |
6 | 5 | 2exbii | |
7 | 1 6 | bitr4i | |