Description: Obsolete version of 2on as of 30-Nov-2024. (Contributed by NM, 18-Feb-2004) (Proof shortened by Andrew Salmon, 12-Aug-2011) (Proof modification is discouraged.) (New usage is discouraged.)
Ref | Expression | ||
---|---|---|---|
Assertion | 2onOLD | ⊢ 2o ∈ On |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-2o | ⊢ 2o = suc 1o | |
2 | 1on | ⊢ 1o ∈ On | |
3 | 2 | onsuci | ⊢ suc 1o ∈ On |
4 | 1 3 | eqeltri | ⊢ 2o ∈ On |