Theorem ax8v

Description: Weakened version of ax-8 , with a disjoint variable condition on x , y . This should be the only proof referencing ax-8 , and it should be referenced only by its two weakened versions ax8v1 and ax8v2 , from which ax-8 is then rederived as ax8 , which shows that either ax8v or the conjunction of ax8v1 and ax8v2 is sufficient. (Contributed by BJ, 7-Dec-2020) Use ax8 instead. (New usage is discouraged.)

	Ref	Expression
Assertion	ax8v	$$⊢x=y\to \left(x\in z\to y\in z\right)$$

Proof

Step	Hyp	Ref	Expression
1		ax-8	$$⊢x=y\to \left(x\in z\to y\in z\right)$$