Theorem opthregOLD 8812

Description: Obsolete proof of opthreg 8810 as of 15-Jun-2022. Theorem for alternate representation of ordered pairs, requiring the Axiom of Regularity ax-reg 8786 (via the preleqOLD 8811 step). See df-op 4405 for a description of other ordered pair representations. Exercise 34 of [Enderton] p. 207. (Contributed by NM, 16-Oct-1996.) (Proof modification is discouraged.) (New usage is discouraged.)

Hypotheses

Ref	Expression
opthreg.1	⊢ 𝐴 ∈ V
opthreg.2	⊢ 𝐵 ∈ V
opthreg.3	⊢ 𝐶 ∈ V
opthreg.4	⊢ 𝐷 ∈ V

Assertion

Ref	Expression
opthregOLD	⊢ ({𝐴, {𝐴, 𝐵}} = {𝐶, {𝐶, 𝐷}} ↔ (𝐴 = 𝐶 ∧ 𝐵 = 𝐷))

Proof of Theorem opthregOLD

Step	Hyp	Ref	Expression
1		opthreg.1	. . . . 5 ⊢ 𝐴 ∈ V
2	1	prid1 4529	. . . 4 ⊢ 𝐴 ∈ {𝐴, 𝐵}
3		opthreg.3	. . . . 5 ⊢ 𝐶 ∈ V
4	3	prid1 4529	. . . 4 ⊢ 𝐶 ∈ {𝐶, 𝐷}
5		prex 5141	. . . . 5 ⊢ {𝐴, 𝐵} ∈ V
6		prex 5141	. . . . 5 ⊢ {𝐶, 𝐷} ∈ V
7	1, 5, 3, 6	preleqOLD 8811	. . . 4 ⊢ (((𝐴 ∈ {𝐴, 𝐵} ∧ 𝐶 ∈ {𝐶, 𝐷}) ∧ {𝐴, {𝐴, 𝐵}} = {𝐶, {𝐶, 𝐷}}) → (𝐴 = 𝐶 ∧ {𝐴, 𝐵} = {𝐶, 𝐷}))
8	2, 4, 7	mpanl12 692	. . 3 ⊢ ({𝐴, {𝐴, 𝐵}} = {𝐶, {𝐶, 𝐷}} → (𝐴 = 𝐶 ∧ {𝐴, 𝐵} = {𝐶, 𝐷}))
9		preq1 4500	. . . . . 6 ⊢ (𝐴 = 𝐶 → {𝐴, 𝐵} = {𝐶, 𝐵})
10	9	eqeq1d 2780	. . . . 5 ⊢ (𝐴 = 𝐶 → ({𝐴, 𝐵} = {𝐶, 𝐷} ↔ {𝐶, 𝐵} = {𝐶, 𝐷}))
11		opthreg.2	. . . . . 6 ⊢ 𝐵 ∈ V
12		opthreg.4	. . . . . 6 ⊢ 𝐷 ∈ V
13	11, 12	preqr2 4609	. . . . 5 ⊢ ({𝐶, 𝐵} = {𝐶, 𝐷} → 𝐵 = 𝐷)
14	10, 13	syl6bi 245	. . . 4 ⊢ (𝐴 = 𝐶 → ({𝐴, 𝐵} = {𝐶, 𝐷} → 𝐵 = 𝐷))
15	14	imdistani 564	. . 3 ⊢ ((𝐴 = 𝐶 ∧ {𝐴, 𝐵} = {𝐶, 𝐷}) → (𝐴 = 𝐶 ∧ 𝐵 = 𝐷))
16	8, 15	syl 17	. 2 ⊢ ({𝐴, {𝐴, 𝐵}} = {𝐶, {𝐶, 𝐷}} → (𝐴 = 𝐶 ∧ 𝐵 = 𝐷))
17		preq1 4500	. . . 4 ⊢ (𝐴 = 𝐶 → {𝐴, {𝐴, 𝐵}} = {𝐶, {𝐴, 𝐵}})
18	17	adantr 474	. . 3 ⊢ ((𝐴 = 𝐶 ∧ 𝐵 = 𝐷) → {𝐴, {𝐴, 𝐵}} = {𝐶, {𝐴, 𝐵}})
19		preq12 4502	. . . 4 ⊢ ((𝐴 = 𝐶 ∧ 𝐵 = 𝐷) → {𝐴, 𝐵} = {𝐶, 𝐷})
20	19	preq2d 4507	. . 3 ⊢ ((𝐴 = 𝐶 ∧ 𝐵 = 𝐷) → {𝐶, {𝐴, 𝐵}} = {𝐶, {𝐶, 𝐷}})
21	18, 20	eqtrd 2814	. 2 ⊢ ((𝐴 = 𝐶 ∧ 𝐵 = 𝐷) → {𝐴, {𝐴, 𝐵}} = {𝐶, {𝐶, 𝐷}})
22	16, 21	impbii 201	1 ⊢ ({𝐴, {𝐴, 𝐵}} = {𝐶, {𝐶, 𝐷}} ↔ (𝐴 = 𝐶 ∧ 𝐵 = 𝐷))

Syntax hints:   ↔ wb 198   ∧ wa 386   = wceq 1601   ∈ wcel 2107  Vcvv 3398  {cpr 4400

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1839  ax-4 1853  ax-5 1953  ax-6 2021  ax-7 2055  ax-9 2116  ax-10 2135  ax-11 2150  ax-12 2163  ax-13 2334  ax-ext 2754  ax-sep 5017  ax-nul 5025  ax-pr 5138  ax-reg 8786

This theorem depends on definitions:  df-bi 199  df-an 387  df-or 837  df-3an 1073  df-tru 1605  df-ex 1824  df-nf 1828  df-sb 2012  df-mo 2551  df-eu 2587  df-clab 2764  df-cleq 2770  df-clel 2774  df-nfc 2921  df-ne 2970  df-ral 3095  df-rex 3096  df-rab 3099  df-v 3400  df-sbc 3653  df-dif 3795  df-un 3797  df-in 3799  df-ss 3806  df-nul 4142  df-if 4308  df-sn 4399  df-pr 4401  df-op 4405  df-br 4887  df-opab 4949  df-eprel 5266  df-fr 5314

This theorem is referenced by: (None)