Theorem bj-ax89 32792

Description: A theorem which could be used as sole axiom for the non-logical predicate instead of ax-8 2032 and ax-9 2039. Indeed, it is implied over propositional calculus by the conjunction of ax-8 2032 and ax-9 2039, as proved here. In the other direction, one can prove ax-8 2032 (respectively ax-9 2039) from bj-ax89 32792 by using mpan2 707 ( respectively mpan 706) and equid 1985. (TODO: move to main part.) (Contributed by BJ, 3-Oct-2019.)

Assertion

Ref	Expression
bj-ax89	⊢ ((𝑥 = 𝑦 ∧ 𝑧 = 𝑡) → (𝑥 ∈ 𝑧 → 𝑦 ∈ 𝑡))

Proof of Theorem bj-ax89

Step	Hyp	Ref	Expression
1		ax8 2036	. 2 ⊢ (𝑥 = 𝑦 → (𝑥 ∈ 𝑧 → 𝑦 ∈ 𝑧))
2		ax9 2043	. 2 ⊢ (𝑧 = 𝑡 → (𝑦 ∈ 𝑧 → 𝑦 ∈ 𝑡))
3	1, 2	sylan9 690	1 ⊢ ((𝑥 = 𝑦 ∧ 𝑧 = 𝑡) → (𝑥 ∈ 𝑧 → 𝑦 ∈ 𝑡))

Syntax hints:   → wi 4   ∧ wa 383

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1762  ax-4 1777  ax-5 1879  ax-6 1945  ax-7 1981  ax-8 2032  ax-9 2039

This theorem depends on definitions:  df-bi 197  df-an 385  df-ex 1745

This theorem is referenced by: (None)