Theorem bj-vn0ALT 37817

Description: Alternate proof of vn0 4291 which does not use eqabbw 2833 (and is shorter than vn0 4291 when eqabbw 2833 is inlined). (Contributed by BJ, 12-Jul-2026.) Using the same dummy variable for 𝑦 and 𝑧 slightly reduces the proof size. (Proof modification is discouraged.) (New usage is discouraged.)

Assertion

Ref	Expression
bj-vn0ALT	⊢ V ≠ ∅

Proof of Theorem bj-vn0ALT

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

Step	Hyp	Ref	Expression
1		fal 1584	. . 3 ⊢ ¬ ⊥
2		dfv2 3453	. . . . 5 ⊢ V = {𝑦 ∣ ⊤}
3		dfnul4 4281	. . . . 5 ⊢ ∅ = {𝑧 ∣ ⊥}
4	2, 3	eqeq12i 2778	. . . 4 ⊢ (V = ∅ ↔ {𝑦 ∣ ⊤} = {𝑧 ∣ ⊥})
5		dfcleq 2753	. . . . 5 ⊢ ({𝑦 ∣ ⊤} = {𝑧 ∣ ⊥} ↔ ∀𝑥(𝑥 ∈ {𝑦 ∣ ⊤} ↔ 𝑥 ∈ {𝑧 ∣ ⊥}))
6		df-clab 2739	. . . . . . . . 9 ⊢ (𝑥 ∈ {𝑦 ∣ ⊤} ↔ [𝑥 / 𝑦]⊤)
7		sbv 2125	. . . . . . . . 9 ⊢ ([𝑥 / 𝑦]⊤ ↔ ⊤)
8	6, 7	bitri 278	. . . . . . . 8 ⊢ (𝑥 ∈ {𝑦 ∣ ⊤} ↔ ⊤)
9		df-clab 2739	. . . . . . . . 9 ⊢ (𝑥 ∈ {𝑧 ∣ ⊥} ↔ [𝑥 / 𝑧]⊥)
10		sbv 2125	. . . . . . . . 9 ⊢ ([𝑥 / 𝑧]⊥ ↔ ⊥)
11	9, 10	bitri 278	. . . . . . . 8 ⊢ (𝑥 ∈ {𝑧 ∣ ⊥} ↔ ⊥)
12	8, 11	bibi12i 342	. . . . . . 7 ⊢ ((𝑥 ∈ {𝑦 ∣ ⊤} ↔ 𝑥 ∈ {𝑧 ∣ ⊥}) ↔ (⊤ ↔ ⊥))
13		trubifal 1601	. . . . . . 7 ⊢ ((⊤ ↔ ⊥) ↔ ⊥)
14	12, 13	sylbb 222	. . . . . 6 ⊢ ((𝑥 ∈ {𝑦 ∣ ⊤} ↔ 𝑥 ∈ {𝑧 ∣ ⊥}) → ⊥)
15	14	spsv 2020	. . . . 5 ⊢ (∀𝑥(𝑥 ∈ {𝑦 ∣ ⊤} ↔ 𝑥 ∈ {𝑧 ∣ ⊥}) → ⊥)
16	5, 15	sylbi 220	. . . 4 ⊢ ({𝑦 ∣ ⊤} = {𝑧 ∣ ⊥} → ⊥)
17	4, 16	sylbi 220	. . 3 ⊢ (V = ∅ → ⊥)
18	1, 17	mto 200	. 2 ⊢ ¬ V = ∅
19	18	neir 2958	1 ⊢ V ≠ ∅

This proof depends on syntax axioms:   ↔ wb 209  ∀wal 1568   = wceq 1570  ⊤wtru 1571  ⊥wfal 1582  [wsb 2099   ∈ wcel 2145  {cab 2738   ≠ wne 2955  Vcvv 3450  ∅c0 4279

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1828  ax-4 1842  ax-5 1943  ax-6 2000  ax-7 2041  ax-9 2155  ax-ext 2732

This proof depends on definitions:  df-bi 210  df-an 402  df-tru 1573  df-fal 1583  df-ex 1813  df-sb 2100  df-clab 2739  df-cleq 2752  df-ne 2956  df-v 3452  df-dif 3902  df-nul 4280

This theorem is used by: (None)