Theorem 1oex

Description: Ordinal 1 is a set. (Contributed by BJ, 6-Apr-2019) (Proof shortened by AV, 1-Jul-2022)

	Ref	Expression
Assertion	1oex	|- 1o e. _V

Proof

Step	Hyp	Ref	Expression
1		1on	|- 1o e. On
2	1	elexi	|- 1o e. _V