Description: Expanded value of the ordinal number 1. Definition 2.1 of Schloeder p. 4. (Contributed by NM, 4-Nov-2002)
Ref | Expression | ||
---|---|---|---|
Assertion | df1o2 | ⊢ 1o = { ∅ } |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-1o | ⊢ 1o = suc ∅ | |
2 | suc0 | ⊢ suc ∅ = { ∅ } | |
3 | 1 2 | eqtri | ⊢ 1o = { ∅ } |