Theorem elpreqpr 4794

Description: Equality and membership rule for pairs. (Contributed by Scott Fenton, 7-Dec-2020.)

Assertion

Ref	Expression
elpreqpr	⊢ (𝐴 ∈ {𝐵, 𝐶} → ∃𝑥{𝐵, 𝐶} = {𝐴, 𝑥})

Distinct variable groups:   𝑥,𝐴   𝑥,𝐵   𝑥,𝐶

Proof of Theorem elpreqpr

Step	Hyp	Ref	Expression
1		elpri 4580	. 2 ⊢ (𝐴 ∈ {𝐵, 𝐶} → (𝐴 = 𝐵 ∨ 𝐴 = 𝐶))
2		elex 3440	. 2 ⊢ (𝐴 ∈ {𝐵, 𝐶} → 𝐴 ∈ V)
3		elpreqprlem 4793	. . . . 5 ⊢ (𝐵 ∈ V → ∃𝑥{𝐵, 𝐶} = {𝐵, 𝑥})
4		eleq1 2826	. . . . . 6 ⊢ (𝐴 = 𝐵 → (𝐴 ∈ V ↔ 𝐵 ∈ V))
5		preq1 4666	. . . . . . . 8 ⊢ (𝐴 = 𝐵 → {𝐴, 𝑥} = {𝐵, 𝑥})
6	5	eqeq2d 2749	. . . . . . 7 ⊢ (𝐴 = 𝐵 → ({𝐵, 𝐶} = {𝐴, 𝑥} ↔ {𝐵, 𝐶} = {𝐵, 𝑥}))
7	6	exbidv 1925	. . . . . 6 ⊢ (𝐴 = 𝐵 → (∃𝑥{𝐵, 𝐶} = {𝐴, 𝑥} ↔ ∃𝑥{𝐵, 𝐶} = {𝐵, 𝑥}))
8	4, 7	imbi12d 344	. . . . 5 ⊢ (𝐴 = 𝐵 → ((𝐴 ∈ V → ∃𝑥{𝐵, 𝐶} = {𝐴, 𝑥}) ↔ (𝐵 ∈ V → ∃𝑥{𝐵, 𝐶} = {𝐵, 𝑥})))
9	3, 8	mpbiri 257	. . . 4 ⊢ (𝐴 = 𝐵 → (𝐴 ∈ V → ∃𝑥{𝐵, 𝐶} = {𝐴, 𝑥}))
10	9	imp 406	. . 3 ⊢ ((𝐴 = 𝐵 ∧ 𝐴 ∈ V) → ∃𝑥{𝐵, 𝐶} = {𝐴, 𝑥})
11		elpreqprlem 4793	. . . . . 6 ⊢ (𝐶 ∈ V → ∃𝑥{𝐶, 𝐵} = {𝐶, 𝑥})
12		prcom 4665	. . . . . . . 8 ⊢ {𝐶, 𝐵} = {𝐵, 𝐶}
13	12	eqeq1i 2743	. . . . . . 7 ⊢ ({𝐶, 𝐵} = {𝐶, 𝑥} ↔ {𝐵, 𝐶} = {𝐶, 𝑥})
14	13	exbii 1851	. . . . . 6 ⊢ (∃𝑥{𝐶, 𝐵} = {𝐶, 𝑥} ↔ ∃𝑥{𝐵, 𝐶} = {𝐶, 𝑥})
15	11, 14	sylib 217	. . . . 5 ⊢ (𝐶 ∈ V → ∃𝑥{𝐵, 𝐶} = {𝐶, 𝑥})
16		eleq1 2826	. . . . . 6 ⊢ (𝐴 = 𝐶 → (𝐴 ∈ V ↔ 𝐶 ∈ V))
17		preq1 4666	. . . . . . . 8 ⊢ (𝐴 = 𝐶 → {𝐴, 𝑥} = {𝐶, 𝑥})
18	17	eqeq2d 2749	. . . . . . 7 ⊢ (𝐴 = 𝐶 → ({𝐵, 𝐶} = {𝐴, 𝑥} ↔ {𝐵, 𝐶} = {𝐶, 𝑥}))
19	18	exbidv 1925	. . . . . 6 ⊢ (𝐴 = 𝐶 → (∃𝑥{𝐵, 𝐶} = {𝐴, 𝑥} ↔ ∃𝑥{𝐵, 𝐶} = {𝐶, 𝑥}))
20	16, 19	imbi12d 344	. . . . 5 ⊢ (𝐴 = 𝐶 → ((𝐴 ∈ V → ∃𝑥{𝐵, 𝐶} = {𝐴, 𝑥}) ↔ (𝐶 ∈ V → ∃𝑥{𝐵, 𝐶} = {𝐶, 𝑥})))
21	15, 20	mpbiri 257	. . . 4 ⊢ (𝐴 = 𝐶 → (𝐴 ∈ V → ∃𝑥{𝐵, 𝐶} = {𝐴, 𝑥}))
22	21	imp 406	. . 3 ⊢ ((𝐴 = 𝐶 ∧ 𝐴 ∈ V) → ∃𝑥{𝐵, 𝐶} = {𝐴, 𝑥})
23	10, 22	jaoian 953	. 2 ⊢ (((𝐴 = 𝐵 ∨ 𝐴 = 𝐶) ∧ 𝐴 ∈ V) → ∃𝑥{𝐵, 𝐶} = {𝐴, 𝑥})
24	1, 2, 23	syl2anc 583	1 ⊢ (𝐴 ∈ {𝐵, 𝐶} → ∃𝑥{𝐵, 𝐶} = {𝐴, 𝑥})

Syntax hints:   → wi 4   ∨ wo 843   = wceq 1539  ∃wex 1783   ∈ wcel 2108  Vcvv 3422  {cpr 4560

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1799  ax-4 1813  ax-5 1914  ax-6 1972  ax-7 2012  ax-8 2110  ax-9 2118  ax-ext 2709

This theorem depends on definitions:  df-bi 206  df-an 396  df-or 844  df-tru 1542  df-fal 1552  df-ex 1784  df-sb 2069  df-clab 2716  df-cleq 2730  df-clel 2817  df-v 3424  df-dif 3886  df-un 3888  df-nul 4254  df-sn 4559  df-pr 4561

This theorem is referenced by:  elpreqprb  4795