Theorem rexpr 3761

Description: Convert an 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 3757	. 2 ⊢ ((𝐴 ∈ V ∧ 𝐵 ∈ V) → (∃𝑥 ∈ {𝐴, 𝐵}𝜑 ↔ (𝜓 ∨ 𝜒)))
6	1, 2, 5	mp2an 430	1 ⊢ (∃𝑥 ∈ {𝐴, 𝐵}𝜑 ↔ (𝜓 ∨ 𝜒))

Syntax hints:   → wi 4   ↔ wb 105   ∨ wo 720   = wceq 1402   ∈ wcel 2209  ∃wrex 2529  Vcvv 2821  {cpr 3706

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-io 721  ax-5 1500  ax-7 1501  ax-gen 1502  ax-ie1 1546  ax-ie2 1547  ax-8 1557  ax-10 1558  ax-11 1559  ax-i12 1560  ax-bndl 1562  ax-4 1563  ax-17 1579  ax-i9 1583  ax-ial 1587  ax-i5r 1588  ax-ext 2220

This theorem depends on definitions:  df-bi 117  df-3an 1011  df-tru 1405  df-nf 1514  df-sb 1816  df-clab 2225  df-cleq 2231  df-clel 2234  df-nfc 2381  df-rex 2534  df-v 2823  df-sbc 3052  df-un 3224  df-sn 3711  df-pr 3712

This theorem is referenced by: (None)