Theorem bj-ax89 37329

Description: A theorem which could be used as sole axiom for the non-logical predicate instead of ax-8 2144 and ax-9 2152. Indeed, it is implied over propositional calculus by the conjunction of ax-8 2144 and ax-9 2152, as proved here. In the other direction, one can prove ax-8 2144 (respectively ax-9 2152) from bj-ax89 37329 by using mpan2 703 (respectively mpan 702) and equid 2041. 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 2148	. 2 ⊢ (𝑥 = 𝑦 → (𝑥 ∈ 𝑧 → 𝑦 ∈ 𝑧))
2		ax9 2156	. 2 ⊢ (𝑧 = 𝑡 → (𝑦 ∈ 𝑧 → 𝑦 ∈ 𝑡))
3	1, 2	sylan9 516	1 ⊢ ((𝑥 = 𝑦 ∧ 𝑧 = 𝑡) → (𝑥 ∈ 𝑧 → 𝑦 ∈ 𝑡))

This proof depends on syntax axioms:   → wi 4   ∧ wa 400

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1824  ax-4 1838  ax-5 1939  ax-6 1996  ax-7 2037  ax-8 2144  ax-9 2152

This proof depends on definitions:  df-bi 210  df-an 401  df-ex 1809

This theorem is used by: (None)