Theorem reueubd 3388

Description: Restricted existential uniqueness is equivalent to existential uniqueness if the unique element is in the restricting class. (Contributed by AV, 4-Jan-2021.)

Hypothesis

Ref	Expression
reueubd.1	⊢ ((𝜑 ∧ 𝜓) → 𝑥 ∈ 𝑉)

Assertion

Ref	Expression
reueubd	⊢ (𝜑 → (∃!𝑥 ∈ 𝑉 𝜓 ↔ ∃!𝑥𝜓))

Distinct variable group:   𝜑,𝑥

Allowed substitution hints:   𝜓(𝑥)   𝑉(𝑥)

Proof of Theorem reueubd

Step	Hyp	Ref	Expression
1		df-reu 3372	. 2 ⊢ (∃!𝑥 ∈ 𝑉 𝜓 ↔ ∃!𝑥(𝑥 ∈ 𝑉 ∧ 𝜓))
2		reueubd.1	. . . . 5 ⊢ ((𝜑 ∧ 𝜓) → 𝑥 ∈ 𝑉)
3	2	ex 418	. . . 4 ⊢ (𝜑 → (𝜓 → 𝑥 ∈ 𝑉))
4	3	pm4.71rd 572	. . 3 ⊢ (𝜑 → (𝜓 ↔ (𝑥 ∈ 𝑉 ∧ 𝜓)))
5	4	eubidv 2616	. 2 ⊢ (𝜑 → (∃!𝑥𝜓 ↔ ∃!𝑥(𝑥 ∈ 𝑉 ∧ 𝜓)))
6	1, 5	bitr4id 293	1 ⊢ (𝜑 → (∃!𝑥 ∈ 𝑉 𝜓 ↔ ∃!𝑥𝜓))

This proof depends on syntax axioms:   → wi 4   ↔ wb 209   ∧ wa 401   ∈ wcel 2146  ∃!weu 2598  ∃!wreu 3369

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1828  ax-4 1842  ax-5 1943  ax-6 2000  ax-7 2041

This proof depends on definitions:  df-bi 210  df-an 402  df-ex 1813  df-mo 2569  df-eu 2599  df-reu 3372

This theorem is used by:  frgreu  30692  modelac8prim  45761