Theorem ax8v 1980

Description: Weakened version of ax-8 1979, with a dv condition on 𝑥, 𝑦. This should be the only proof referencing ax-8 1979, and it should be referenced only by its two weakened versions ax8v1 1981 and ax8v2 1982, from which ax-8 1979 is then rederived as ax8 1983, which shows that either ax8v 1980 or the conjunction of ax8v1 1981 and ax8v2 1982 is sufficient. (Contributed by BJ, 7-Dec-2020.) Use ax8 1983 instead. (New usage is discouraged.)

Assertion

Ref	Expression
ax8v	⊢ (𝑥 = 𝑦 → (𝑥 ∈ 𝑧 → 𝑦 ∈ 𝑧))

Distinct variable group:   𝑥,𝑦

Proof of Theorem ax8v

Step	Hyp	Ref	Expression
1		ax-8 1979	1 ⊢ (𝑥 = 𝑦 → (𝑥 ∈ 𝑧 → 𝑦 ∈ 𝑧))

Syntax hints:   → wi 4

This theorem was proved from axioms:  ax-8 1979

This theorem is referenced by:  ax8v1  1981  ax8v2  1982