Description: Obsolete version of 2oex as of 19-Sep-2024. (Contributed by BJ, 6-Apr-2019) (Proof modification is discouraged.) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | 2oexOLD | |- 2o e. _V |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | df-2o | |- 2o = suc 1o |
|
| 2 | 1oex | |- 1o e. _V |
|
| 3 | 2 | sucex | |- suc 1o e. _V |
| 4 | 1 3 | eqeltri | |- 2o e. _V |