Description: The empty set is an ordinal number. Corollary 7N(b) of Enderton p. 193. Remark 1.5 of Schloeder p. 1. (Contributed by NM, 17-Sep-1993)
Ref | Expression | ||
---|---|---|---|
Assertion | 0elon |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ord0 | ||
2 | 0ex | ||
3 | 2 | elon | |
4 | 1 3 | mpbir |