Theorem ax9v1 2001

Description: First of two weakened versions of ax9v 2000, with an extra dv condition on x , z, see comments there. (Contributed by BJ, 7-Dec-2020.)

Assertion

Ref	Expression
ax9v1	|- ( x = y -> ( z e. x -> z e. y ) )

Distinct variable groups:   x, y   x, z

Proof of Theorem ax9v1

Step	Hyp	Ref	Expression
1		ax9v 2000	1 |- ( x = y -> ( z e. x -> z e. y ) )

Syntax hints:   -> wi 4

This theorem was proved from axioms:  ax-9 1999

This theorem is referenced by:  ax9  2003