Theorem rexpr 4662

Description: Convert a restricted existential quantification over a pair to a disjunction. (Contributed by NM, 3-Jun-2007.) (Revised by Mario Carneiro, 23-Apr-2015.)

Hypotheses

Ref	Expression
ralpr.1	⊢ 𝐴 ∈ V
ralpr.2	⊢ 𝐵 ∈ V
ralpr.3	⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜓))
ralpr.4	⊢ (𝑥 = 𝐵 → (𝜑 ↔ 𝜒))

Assertion

Ref	Expression
rexpr	⊢ (∃𝑥 ∈ {𝐴, 𝐵}𝜑 ↔ (𝜓 ∨ 𝜒))

Distinct variable groups:   𝑥,𝐴   𝑥,𝐵   𝜓,𝑥   𝜒,𝑥

Allowed substitution hint:   𝜑(𝑥)

Proof of Theorem rexpr

Step	Hyp	Ref	Expression
1		ralpr.1	. 2 ⊢ 𝐴 ∈ V
2		ralpr.2	. 2 ⊢ 𝐵 ∈ V
3		ralpr.3	. . 3 ⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜓))
4		ralpr.4	. . 3 ⊢ (𝑥 = 𝐵 → (𝜑 ↔ 𝜒))
5	3, 4	rexprg 4658	. 2 ⊢ ((𝐴 ∈ V ∧ 𝐵 ∈ V) → (∃𝑥 ∈ {𝐴, 𝐵}𝜑 ↔ (𝜓 ∨ 𝜒)))
6	1, 2, 5	mp2an 705	1 ⊢ (∃𝑥 ∈ {𝐴, 𝐵}𝜑 ↔ (𝜓 ∨ 𝜒))

This proof depends on syntax axioms:   → wi 4   ↔ wb 209   ∨ wo 861   = wceq 1570   ∈ wcel 2147  ∃wrex 3090  Vcvv 3454  {cpr 4590

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 1945  ax-6 2002  ax-7 2043  ax-8 2149  ax-9 2157  ax-ext 2735

This proof depends on definitions:  df-bi 210  df-an 402  df-or 862  df-tru 1573  df-ex 1813  df-sb 2102  df-clab 2742  df-cleq 2755  df-clel 2839  df-ral 3081  df-rex 3091  df-v 3456  df-un 4154  df-sn 4589  df-pr 4591

This theorem is used by:  xpsdsval  24727  poimir  38762