Theorem eq0OLDOLD

Description: Obsolete version of eq0 as of 28-Jun-2024. (Contributed by NM, 29-Aug-1993) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	eq0OLDOLD	$$⊢A=\varnothing \leftrightarrow \forall x\neg x\in A$$

Proof

Step	Hyp	Ref	Expression
1		nfcv	$$⊢\underset{\_}{Ⅎ}xA$$
2	1	eq0f	$$⊢A=\varnothing \leftrightarrow \forall x\neg x\in A$$