Description: One of the two elements in an ordered pair. (Contributed by NM, 15-Jul-1993) (Revised by Mario Carneiro, 26-Apr-2015) (Avoid depending on this detail.)
Ref | Expression | ||
---|---|---|---|
Hypotheses | opi1.1 | |- A e. _V |
|
opi1.2 | |- B e. _V |
||
Assertion | opi1 | |- { A } e. <. A , B >. |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | opi1.1 | |- A e. _V |
|
2 | opi1.2 | |- B e. _V |
|
3 | snex | |- { A } e. _V |
|
4 | 3 | prid1 | |- { A } e. { { A } , { A , B } } |
5 | 1 2 | dfop | |- <. A , B >. = { { A } , { A , B } } |
6 | 4 5 | eleqtrri | |- { A } e. <. A , B >. |