Theorem cnv0 5857

Description: The converse of the empty set. (Contributed by NM, 6-Apr-1998.) Remove dependency on ax-sep 5248, ax-nul 5258, ax-pr 5392. (Revised by KP, 25-Oct-2021.) Avoid ax-12 2214. (Revised by TM, 31-Jan-2026.)

Assertion

Ref	Expression
cnv0	⊢ ◡∅ = ∅

Proof of Theorem cnv0

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

Step	Hyp	Ref	Expression
1		br0 5151	. . . . . 6 ⊢ ¬ 𝑦∅𝑧
2	1	intnan 490	. . . . 5 ⊢ ¬ (𝑥 = ⟨𝑧, 𝑦⟩ ∧ 𝑦∅𝑧)
3	2	nex 1822	. . . 4 ⊢ ¬ ∃𝑦(𝑥 = ⟨𝑧, 𝑦⟩ ∧ 𝑦∅𝑧)
4	3	nex 1822	. . 3 ⊢ ¬ ∃𝑧∃𝑦(𝑥 = ⟨𝑧, 𝑦⟩ ∧ 𝑦∅𝑧)
5		df-cnv 5657	. . . . 5 ⊢ ◡∅ = {⟨𝑧, 𝑦⟩ ∣ 𝑦∅𝑧}
6	5	eleq2i 2856	. . . 4 ⊢ (𝑥 ∈ ◡∅ ↔ 𝑥 ∈ {⟨𝑧, 𝑦⟩ ∣ 𝑦∅𝑧})
7		elopabw 5498	. . . . 5 ⊢ (𝑥 ∈ V → (𝑥 ∈ {⟨𝑧, 𝑦⟩ ∣ 𝑦∅𝑧} ↔ ∃𝑧∃𝑦(𝑥 = ⟨𝑧, 𝑦⟩ ∧ 𝑦∅𝑧)))
8	7	elv 3461	. . . 4 ⊢ (𝑥 ∈ {⟨𝑧, 𝑦⟩ ∣ 𝑦∅𝑧} ↔ ∃𝑧∃𝑦(𝑥 = ⟨𝑧, 𝑦⟩ ∧ 𝑦∅𝑧))
9	6, 8	bitri 277	. . 3 ⊢ (𝑥 ∈ ◡∅ ↔ ∃𝑧∃𝑦(𝑥 = ⟨𝑧, 𝑦⟩ ∧ 𝑦∅𝑧))
10	4, 9	mtbir 325	. 2 ⊢ ¬ 𝑥 ∈ ◡∅
11	10	nel0 4309	1 ⊢ ◡∅ = ∅

Syntax hints:   ↔ wb 208   ∧ wa 399   = wceq 1562  ∃wex 1801   ∈ wcel 2144  Vcvv 3456  ∅c0 4287  ⟨cop 4590   class class class wbr 5102  {copab 5164  ^◡ccnv 5648

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1817  ax-4 1831  ax-5 1932  ax-6 1989  ax-7 2030  ax-8 2146  ax-9 2154  ax-ext 2736

This theorem depends on definitions:  df-bi 209  df-an 400  df-tru 1565  df-fal 1575  df-ex 1802  df-sb 2093  df-clab 2743  df-cleq 2756  df-clel 2839  df-v 3458  df-dif 3909  df-nul 4288  df-br 5103  df-opab 5165  df-cnv 5657

This theorem is referenced by:  csbcnv  5860  xp0OLD  6145  cnveq0  6186  co01  6251  funcnv0  6589  f1o00  6844  tpos0  8238  cnvfi  9146  oduleval  18323  ust0  24282  nghmfval  24784  isnghm  24785  1pthdlem1  30339  mptiffisupp  32897  tocycf  33299  tocyc01  33300  vieta  33879  mthmval  35930  resnonrel  44173  cononrel1  44175  cononrel2  44176  cnvrcl0  44206  0cnf  46456