Theorem ax9v1

Description: First of two weakened versions of ax9v , with an extra disjoint variable condition on x , z , see comments there. (Contributed by BJ, 7-Dec-2020)

	Ref	Expression
Assertion	ax9v1	$$⊢x=y\to \left(z\in x\to z\in y\right)$$

Proof

Step	Hyp	Ref	Expression
1		ax9v	$$⊢x=y\to \left(z\in x\to z\in y\right)$$