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Theorem ax9v2 1989
Description: Second of two weakened versions of ax9v 1987, with an extra dv condition on 𝑦, 𝑧 see comments there. (Contributed by BJ, 7-Dec-2020.)
Ref Expression
ax9v2 (𝑥 = 𝑦 → (𝑧𝑥𝑧𝑦))
Distinct variable groups:   𝑥,𝑦   𝑦,𝑧

Proof of Theorem ax9v2
StepHypRef Expression
1 ax9v 1987 1 (𝑥 = 𝑦 → (𝑧𝑥𝑧𝑦))
Colors of variables: wff setvar class
Syntax hints:  wi 4
This theorem was proved from axioms:  ax-9 1986
This theorem is referenced by:  ax9  1990
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