Theorem dtruOLD 5452

Description: Obsolete version of dtru 5447 as of 01-Jan-2025. (Contributed by NM, 7-Nov-2006.) Avoid ax-13 2375. (Revised by BJ, 31-May-2019.) Avoid ax-12 2175. (Revised by Rohan Ridenour, 9-Oct-2024.) Use ax-pr 5438 instead of ax-pow 5371. (Revised by BTernaryTau, 3-Dec-2024.) (Proof modification is discouraged.) (New usage is discouraged.)

Assertion

Ref	Expression
dtruOLD	⊢ ¬ ∀𝑥 𝑥 = 𝑦

Distinct variable group:   𝑥,𝑦

Proof of Theorem dtruOLD

Dummy variables 𝑤 𝑧 are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		el 5448	. . . 4 ⊢ ∃𝑤 𝑥 ∈ 𝑤
2		ax-nul 5312	. . . . 5 ⊢ ∃𝑧∀𝑥 ¬ 𝑥 ∈ 𝑧
3		elequ1 2113	. . . . . . 7 ⊢ (𝑥 = 𝑤 → (𝑥 ∈ 𝑧 ↔ 𝑤 ∈ 𝑧))
4	3	notbid 318	. . . . . 6 ⊢ (𝑥 = 𝑤 → (¬ 𝑥 ∈ 𝑧 ↔ ¬ 𝑤 ∈ 𝑧))
5	4	spw 2031	. . . . 5 ⊢ (∀𝑥 ¬ 𝑥 ∈ 𝑧 → ¬ 𝑥 ∈ 𝑧)
6	2, 5	eximii 1834	. . . 4 ⊢ ∃𝑧 ¬ 𝑥 ∈ 𝑧
7		exdistrv 1953	. . . 4 ⊢ (∃𝑤∃𝑧(𝑥 ∈ 𝑤 ∧ ¬ 𝑥 ∈ 𝑧) ↔ (∃𝑤 𝑥 ∈ 𝑤 ∧ ∃𝑧 ¬ 𝑥 ∈ 𝑧))
8	1, 6, 7	mpbir2an 711	. . 3 ⊢ ∃𝑤∃𝑧(𝑥 ∈ 𝑤 ∧ ¬ 𝑥 ∈ 𝑧)
9		ax9v2 2119	. . . . . 6 ⊢ (𝑤 = 𝑧 → (𝑥 ∈ 𝑤 → 𝑥 ∈ 𝑧))
10	9	com12 32	. . . . 5 ⊢ (𝑥 ∈ 𝑤 → (𝑤 = 𝑧 → 𝑥 ∈ 𝑧))
11	10	con3dimp 408	. . . 4 ⊢ ((𝑥 ∈ 𝑤 ∧ ¬ 𝑥 ∈ 𝑧) → ¬ 𝑤 = 𝑧)
12	11	2eximi 1833	. . 3 ⊢ (∃𝑤∃𝑧(𝑥 ∈ 𝑤 ∧ ¬ 𝑥 ∈ 𝑧) → ∃𝑤∃𝑧 ¬ 𝑤 = 𝑧)
13		equequ2 2023	. . . . . . 7 ⊢ (𝑧 = 𝑦 → (𝑤 = 𝑧 ↔ 𝑤 = 𝑦))
14	13	notbid 318	. . . . . 6 ⊢ (𝑧 = 𝑦 → (¬ 𝑤 = 𝑧 ↔ ¬ 𝑤 = 𝑦))
15		ax7v1 2007	. . . . . . . 8 ⊢ (𝑥 = 𝑤 → (𝑥 = 𝑦 → 𝑤 = 𝑦))
16	15	con3d 152	. . . . . . 7 ⊢ (𝑥 = 𝑤 → (¬ 𝑤 = 𝑦 → ¬ 𝑥 = 𝑦))
17	16	spimevw 1992	. . . . . 6 ⊢ (¬ 𝑤 = 𝑦 → ∃𝑥 ¬ 𝑥 = 𝑦)
18	14, 17	biimtrdi 253	. . . . 5 ⊢ (𝑧 = 𝑦 → (¬ 𝑤 = 𝑧 → ∃𝑥 ¬ 𝑥 = 𝑦))
19		ax7v1 2007	. . . . . . . 8 ⊢ (𝑥 = 𝑧 → (𝑥 = 𝑦 → 𝑧 = 𝑦))
20	19	con3d 152	. . . . . . 7 ⊢ (𝑥 = 𝑧 → (¬ 𝑧 = 𝑦 → ¬ 𝑥 = 𝑦))
21	20	spimevw 1992	. . . . . 6 ⊢ (¬ 𝑧 = 𝑦 → ∃𝑥 ¬ 𝑥 = 𝑦)
22	21	a1d 25	. . . . 5 ⊢ (¬ 𝑧 = 𝑦 → (¬ 𝑤 = 𝑧 → ∃𝑥 ¬ 𝑥 = 𝑦))
23	18, 22	pm2.61i 182	. . . 4 ⊢ (¬ 𝑤 = 𝑧 → ∃𝑥 ¬ 𝑥 = 𝑦)
24	23	exlimivv 1930	. . 3 ⊢ (∃𝑤∃𝑧 ¬ 𝑤 = 𝑧 → ∃𝑥 ¬ 𝑥 = 𝑦)
25	8, 12, 24	mp2b 10	. 2 ⊢ ∃𝑥 ¬ 𝑥 = 𝑦
26		exnal 1824	. 2 ⊢ (∃𝑥 ¬ 𝑥 = 𝑦 ↔ ¬ ∀𝑥 𝑥 = 𝑦)
27	25, 26	mpbi 230	1 ⊢ ¬ ∀𝑥 𝑥 = 𝑦

Syntax hints:  ¬ wn 3   → wi 4   ∧ wa 395  ∀wal 1535  ∃wex 1776

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1792  ax-4 1806  ax-5 1908  ax-6 1965  ax-7 2005  ax-8 2108  ax-9 2116  ax-nul 5312  ax-pr 5438

This theorem depends on definitions:  df-bi 207  df-an 396  df-or 848  df-ex 1777

This theorem is referenced by: (None)