Theorem dfinfre 12191

Description: The infimum of a set of reals 𝐴. (Contributed by NM, 9-Oct-2005.) (Revised by AV, 4-Sep-2020.)

Assertion

Ref	Expression
dfinfre	⊢ (𝐴 ⊆ ℝ → inf(𝐴, ℝ, < ) = ∪ {𝑥 ∈ ℝ ∣ (∀𝑦 ∈ 𝐴 𝑥 ≤ 𝑦 ∧ ∀𝑦 ∈ ℝ (𝑥 < 𝑦 → ∃𝑧 ∈ 𝐴 𝑧 < 𝑦))})

Distinct variable group:   𝑥,𝐴,𝑦,𝑧

Proof of Theorem dfinfre

Step	Hyp	Ref	Expression
1		df-inf 9434	. 2 ⊢ inf(𝐴, ℝ, < ) = sup(𝐴, ℝ, ◡ < )
2		df-sup 9433	. . 3 ⊢ sup(𝐴, ℝ, ◡ < ) = ∪ {𝑥 ∈ ℝ ∣ (∀𝑦 ∈ 𝐴 ¬ 𝑥◡ < 𝑦 ∧ ∀𝑦 ∈ ℝ (𝑦◡ < 𝑥 → ∃𝑧 ∈ 𝐴 𝑦◡ < 𝑧))}
3		ssel2 3976	. . . . . . . . . 10 ⊢ ((𝐴 ⊆ ℝ ∧ 𝑦 ∈ 𝐴) → 𝑦 ∈ ℝ)
4		vex 3478	. . . . . . . . . . . . 13 ⊢ 𝑥 ∈ V
5		vex 3478	. . . . . . . . . . . . 13 ⊢ 𝑦 ∈ V
6	4, 5	brcnv 5880	. . . . . . . . . . . 12 ⊢ (𝑥◡ < 𝑦 ↔ 𝑦 < 𝑥)
7	6	notbii 319	. . . . . . . . . . 11 ⊢ (¬ 𝑥◡ < 𝑦 ↔ ¬ 𝑦 < 𝑥)
8		lenlt 11288	. . . . . . . . . . 11 ⊢ ((𝑥 ∈ ℝ ∧ 𝑦 ∈ ℝ) → (𝑥 ≤ 𝑦 ↔ ¬ 𝑦 < 𝑥))
9	7, 8	bitr4id 289	. . . . . . . . . 10 ⊢ ((𝑥 ∈ ℝ ∧ 𝑦 ∈ ℝ) → (¬ 𝑥◡ < 𝑦 ↔ 𝑥 ≤ 𝑦))
10	3, 9	sylan2 593	. . . . . . . . 9 ⊢ ((𝑥 ∈ ℝ ∧ (𝐴 ⊆ ℝ ∧ 𝑦 ∈ 𝐴)) → (¬ 𝑥◡ < 𝑦 ↔ 𝑥 ≤ 𝑦))
11	10	ancoms 459	. . . . . . . 8 ⊢ (((𝐴 ⊆ ℝ ∧ 𝑦 ∈ 𝐴) ∧ 𝑥 ∈ ℝ) → (¬ 𝑥◡ < 𝑦 ↔ 𝑥 ≤ 𝑦))
12	11	an32s 650	. . . . . . 7 ⊢ (((𝐴 ⊆ ℝ ∧ 𝑥 ∈ ℝ) ∧ 𝑦 ∈ 𝐴) → (¬ 𝑥◡ < 𝑦 ↔ 𝑥 ≤ 𝑦))
13	12	ralbidva 3175	. . . . . 6 ⊢ ((𝐴 ⊆ ℝ ∧ 𝑥 ∈ ℝ) → (∀𝑦 ∈ 𝐴 ¬ 𝑥◡ < 𝑦 ↔ ∀𝑦 ∈ 𝐴 𝑥 ≤ 𝑦))
14	5, 4	brcnv 5880	. . . . . . . . 9 ⊢ (𝑦◡ < 𝑥 ↔ 𝑥 < 𝑦)
15		vex 3478	. . . . . . . . . . 11 ⊢ 𝑧 ∈ V
16	5, 15	brcnv 5880	. . . . . . . . . 10 ⊢ (𝑦◡ < 𝑧 ↔ 𝑧 < 𝑦)
17	16	rexbii 3094	. . . . . . . . 9 ⊢ (∃𝑧 ∈ 𝐴 𝑦◡ < 𝑧 ↔ ∃𝑧 ∈ 𝐴 𝑧 < 𝑦)
18	14, 17	imbi12i 350	. . . . . . . 8 ⊢ ((𝑦◡ < 𝑥 → ∃𝑧 ∈ 𝐴 𝑦◡ < 𝑧) ↔ (𝑥 < 𝑦 → ∃𝑧 ∈ 𝐴 𝑧 < 𝑦))
19	18	ralbii 3093	. . . . . . 7 ⊢ (∀𝑦 ∈ ℝ (𝑦◡ < 𝑥 → ∃𝑧 ∈ 𝐴 𝑦◡ < 𝑧) ↔ ∀𝑦 ∈ ℝ (𝑥 < 𝑦 → ∃𝑧 ∈ 𝐴 𝑧 < 𝑦))
20	19	a1i 11	. . . . . 6 ⊢ ((𝐴 ⊆ ℝ ∧ 𝑥 ∈ ℝ) → (∀𝑦 ∈ ℝ (𝑦◡ < 𝑥 → ∃𝑧 ∈ 𝐴 𝑦◡ < 𝑧) ↔ ∀𝑦 ∈ ℝ (𝑥 < 𝑦 → ∃𝑧 ∈ 𝐴 𝑧 < 𝑦)))
21	13, 20	anbi12d 631	. . . . 5 ⊢ ((𝐴 ⊆ ℝ ∧ 𝑥 ∈ ℝ) → ((∀𝑦 ∈ 𝐴 ¬ 𝑥◡ < 𝑦 ∧ ∀𝑦 ∈ ℝ (𝑦◡ < 𝑥 → ∃𝑧 ∈ 𝐴 𝑦◡ < 𝑧)) ↔ (∀𝑦 ∈ 𝐴 𝑥 ≤ 𝑦 ∧ ∀𝑦 ∈ ℝ (𝑥 < 𝑦 → ∃𝑧 ∈ 𝐴 𝑧 < 𝑦))))
22	21	rabbidva 3439	. . . 4 ⊢ (𝐴 ⊆ ℝ → {𝑥 ∈ ℝ ∣ (∀𝑦 ∈ 𝐴 ¬ 𝑥◡ < 𝑦 ∧ ∀𝑦 ∈ ℝ (𝑦◡ < 𝑥 → ∃𝑧 ∈ 𝐴 𝑦◡ < 𝑧))} = {𝑥 ∈ ℝ ∣ (∀𝑦 ∈ 𝐴 𝑥 ≤ 𝑦 ∧ ∀𝑦 ∈ ℝ (𝑥 < 𝑦 → ∃𝑧 ∈ 𝐴 𝑧 < 𝑦))})
23	22	unieqd 4921	. . 3 ⊢ (𝐴 ⊆ ℝ → ∪ {𝑥 ∈ ℝ ∣ (∀𝑦 ∈ 𝐴 ¬ 𝑥◡ < 𝑦 ∧ ∀𝑦 ∈ ℝ (𝑦◡ < 𝑥 → ∃𝑧 ∈ 𝐴 𝑦◡ < 𝑧))} = ∪ {𝑥 ∈ ℝ ∣ (∀𝑦 ∈ 𝐴 𝑥 ≤ 𝑦 ∧ ∀𝑦 ∈ ℝ (𝑥 < 𝑦 → ∃𝑧 ∈ 𝐴 𝑧 < 𝑦))})
24	2, 23	eqtrid 2784	. 2 ⊢ (𝐴 ⊆ ℝ → sup(𝐴, ℝ, ◡ < ) = ∪ {𝑥 ∈ ℝ ∣ (∀𝑦 ∈ 𝐴 𝑥 ≤ 𝑦 ∧ ∀𝑦 ∈ ℝ (𝑥 < 𝑦 → ∃𝑧 ∈ 𝐴 𝑧 < 𝑦))})
25	1, 24	eqtrid 2784	1 ⊢ (𝐴 ⊆ ℝ → inf(𝐴, ℝ, < ) = ∪ {𝑥 ∈ ℝ ∣ (∀𝑦 ∈ 𝐴 𝑥 ≤ 𝑦 ∧ ∀𝑦 ∈ ℝ (𝑥 < 𝑦 → ∃𝑧 ∈ 𝐴 𝑧 < 𝑦))})

Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 205   ∧ wa 396   = wceq 1541   ∈ wcel 2106  ∀wral 3061  ∃wrex 3070  {crab 3432   ⊆ wss 3947  ∪ cuni 4907   class class class wbr 5147  ^◡ccnv 5674  supcsup 9431  infcinf 9432  ℝcr 11105   < clt 11244   ≤ cle 11245

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1913  ax-6 1971  ax-7 2011  ax-8 2108  ax-9 2116  ax-ext 2703  ax-sep 5298  ax-nul 5305  ax-pr 5426

This theorem depends on definitions:  df-bi 206  df-an 397  df-or 846  df-3an 1089  df-tru 1544  df-fal 1554  df-ex 1782  df-sb 2068  df-clab 2710  df-cleq 2724  df-clel 2810  df-ral 3062  df-rex 3071  df-rab 3433  df-v 3476  df-dif 3950  df-un 3952  df-in 3954  df-ss 3964  df-nul 4322  df-if 4528  df-sn 4628  df-pr 4630  df-op 4634  df-uni 4908  df-br 5148  df-opab 5210  df-xp 5681  df-cnv 5683  df-sup 9433  df-inf 9434  df-xr 11248  df-le 11250

This theorem is referenced by: (None)