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Metamath Proof Explorer

Theorem 3on

Description: Ordinal 3 is an ordinal number. (Contributed by Mario Carneiro, 5-Jan-2016)

		Ref	Expression
	Assertion	3on	⊢ 3_o ∈ On

Step	Hyp	Ref	Expression
1		df-3o	⊢ 3_o = suc 2_o
2		2on	⊢ 2_o ∈ On
3	2	onsuci	⊢ suc 2_o ∈ On
4	1 3	eqeltri	⊢ 3_o ∈ On