Theorem cfonOLD

Description: Obsolete version of cfon as of 10-Jun-2026. (Contributed by Mario Carneiro, 9-Mar-2013) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	cfonOLD	⊢ ( cf ‘ 𝐴 ) ∈ On

Proof

Step	Hyp	Ref	Expression
1		cardcf	⊢ ( card ‘ ( cf ‘ 𝐴 ) ) = ( cf ‘ 𝐴 )
2		cardon	⊢ ( card ‘ ( cf ‘ 𝐴 ) ) ∈ On
3	1 2	eqeltrri	⊢ ( cf ‘ 𝐴 ) ∈ On