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Database
CLASSICAL FIRST-ORDER LOGIC WITH EQUALITY
Predicate calculus with equality: Tarski's system S2 (1 rule, 6 schemes)
Axiom scheme ax-5 (Distinctness) - first use of $d
19.41v
Metamath Proof Explorer
Description: Version of 19.41 with a disjoint variable condition, requiring fewer
axioms. (Contributed by NM , 21-Jun-1993) Remove dependency on
ax-6 . (Revised by Rohan Ridenour , 15-Apr-2022)
Ref
Expression
Assertion
19.41v
⊢ ∃ x φ ∧ ψ ↔ ∃ x φ ∧ ψ
Proof
Step
Hyp
Ref
Expression
1
19.40
⊢ ∃ x φ ∧ ψ → ∃ x φ ∧ ∃ x ψ
2
ax5e
⊢ ∃ x ψ → ψ
3
2
anim2i
⊢ ∃ x φ ∧ ∃ x ψ → ∃ x φ ∧ ψ
4
1 3
syl
⊢ ∃ x φ ∧ ψ → ∃ x φ ∧ ψ
5
pm3.21
⊢ ψ → φ → φ ∧ ψ
6
5
eximdv
⊢ ψ → ∃ x φ → ∃ x φ ∧ ψ
7
6
impcom
⊢ ∃ x φ ∧ ψ → ∃ x φ ∧ ψ
8
4 7
impbii
⊢ ∃ x φ ∧ ψ ↔ ∃ x φ ∧ ψ