Theorem noelOLD 4361

Description: Obsolete version of noel 4360 as of 18-Sep-2024. (Contributed by NM, 21-Jun-1993.) (Proof modification is discouraged.) (New usage is discouraged.)

Assertion

Ref	Expression
noelOLD	⊢ ¬ 𝐴 ∈ ∅

Proof of Theorem noelOLD

Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		pm3.24 402	. . . . . . 7 ⊢ ¬ (𝑦 ∈ V ∧ ¬ 𝑦 ∈ V)
2	1	nex 1798	. . . . . 6 ⊢ ¬ ∃𝑦(𝑦 ∈ V ∧ ¬ 𝑦 ∈ V)
3		df-clab 2718	. . . . . . 7 ⊢ (𝑥 ∈ {𝑦 ∣ (𝑦 ∈ V ∧ ¬ 𝑦 ∈ V)} ↔ [𝑥 / 𝑦](𝑦 ∈ V ∧ ¬ 𝑦 ∈ V))
4		spsbe 2082	. . . . . . 7 ⊢ ([𝑥 / 𝑦](𝑦 ∈ V ∧ ¬ 𝑦 ∈ V) → ∃𝑦(𝑦 ∈ V ∧ ¬ 𝑦 ∈ V))
5	3, 4	sylbi 217	. . . . . 6 ⊢ (𝑥 ∈ {𝑦 ∣ (𝑦 ∈ V ∧ ¬ 𝑦 ∈ V)} → ∃𝑦(𝑦 ∈ V ∧ ¬ 𝑦 ∈ V))
6	2, 5	mto 197	. . . . 5 ⊢ ¬ 𝑥 ∈ {𝑦 ∣ (𝑦 ∈ V ∧ ¬ 𝑦 ∈ V)}
7		df-nul 4353	. . . . . . 7 ⊢ ∅ = (V ∖ V)
8		df-dif 3979	. . . . . . 7 ⊢ (V ∖ V) = {𝑦 ∣ (𝑦 ∈ V ∧ ¬ 𝑦 ∈ V)}
9	7, 8	eqtri 2768	. . . . . 6 ⊢ ∅ = {𝑦 ∣ (𝑦 ∈ V ∧ ¬ 𝑦 ∈ V)}
10	9	eleq2i 2836	. . . . 5 ⊢ (𝑥 ∈ ∅ ↔ 𝑥 ∈ {𝑦 ∣ (𝑦 ∈ V ∧ ¬ 𝑦 ∈ V)})
11	6, 10	mtbir 323	. . . 4 ⊢ ¬ 𝑥 ∈ ∅
12	11	intnan 486	. . 3 ⊢ ¬ (𝑥 = 𝐴 ∧ 𝑥 ∈ ∅)
13	12	nex 1798	. 2 ⊢ ¬ ∃𝑥(𝑥 = 𝐴 ∧ 𝑥 ∈ ∅)
14		dfclel 2820	. 2 ⊢ (𝐴 ∈ ∅ ↔ ∃𝑥(𝑥 = 𝐴 ∧ 𝑥 ∈ ∅))
15	13, 14	mtbir 323	1 ⊢ ¬ 𝐴 ∈ ∅

Syntax hints:  ¬ wn 3   ∧ wa 395   = wceq 1537  ∃wex 1777  [wsb 2064   ∈ wcel 2108  {cab 2717  Vcvv 3488   ∖ cdif 3973  ∅c0 4352

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1793  ax-4 1807  ax-5 1909  ax-6 1967  ax-7 2007  ax-8 2110  ax-9 2118  ax-ext 2711

This theorem depends on definitions:  df-bi 207  df-an 396  df-ex 1778  df-sb 2065  df-clab 2718  df-cleq 2732  df-clel 2819  df-dif 3979  df-nul 4353

This theorem is referenced by: (None)