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Theorem limsupreuz 43879
Description: Given a function on the reals, its supremum limit is real if and only if two condition holds: 1. there is a real number that is less than or equal to the function, infinitely often; 2. there is a real number that is greater than or equal to the function. (Contributed by Glauco Siliprandi, 23-Oct-2021.)
Hypotheses
Ref Expression
limsupreuz.1 𝑗𝐹
limsupreuz.2 (𝜑𝑀 ∈ ℤ)
limsupreuz.3 𝑍 = (ℤ𝑀)
limsupreuz.4 (𝜑𝐹:𝑍⟶ℝ)
Assertion
Ref Expression
limsupreuz (𝜑 → ((lim sup‘𝐹) ∈ ℝ ↔ (∃𝑥 ∈ ℝ ∀𝑘𝑍𝑗 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑗) ∧ ∃𝑥 ∈ ℝ ∀𝑗𝑍 (𝐹𝑗) ≤ 𝑥)))
Distinct variable groups:   𝑘,𝐹,𝑥   𝑗,𝑍,𝑘,𝑥
Allowed substitution hints:   𝜑(𝑥,𝑗,𝑘)   𝐹(𝑗)   𝑀(𝑥,𝑗,𝑘)

Proof of Theorem limsupreuz
Dummy variables 𝑖 𝑙 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 nfcv 2905 . . . 4 𝑙𝐹
2 limsupreuz.2 . . . 4 (𝜑𝑀 ∈ ℤ)
3 limsupreuz.3 . . . 4 𝑍 = (ℤ𝑀)
4 limsupreuz.4 . . . . 5 (𝜑𝐹:𝑍⟶ℝ)
54frexr 43524 . . . 4 (𝜑𝐹:𝑍⟶ℝ*)
61, 2, 3, 5limsupre3uzlem 43877 . . 3 (𝜑 → ((lim sup‘𝐹) ∈ ℝ ↔ (∃𝑦 ∈ ℝ ∀𝑖𝑍𝑙 ∈ (ℤ𝑖)𝑦 ≤ (𝐹𝑙) ∧ ∃𝑦 ∈ ℝ ∃𝑖𝑍𝑙 ∈ (ℤ𝑖)(𝐹𝑙) ≤ 𝑦)))
7 breq1 5106 . . . . . . . . 9 (𝑦 = 𝑥 → (𝑦 ≤ (𝐹𝑙) ↔ 𝑥 ≤ (𝐹𝑙)))
87rexbidv 3173 . . . . . . . 8 (𝑦 = 𝑥 → (∃𝑙 ∈ (ℤ𝑖)𝑦 ≤ (𝐹𝑙) ↔ ∃𝑙 ∈ (ℤ𝑖)𝑥 ≤ (𝐹𝑙)))
98ralbidv 3172 . . . . . . 7 (𝑦 = 𝑥 → (∀𝑖𝑍𝑙 ∈ (ℤ𝑖)𝑦 ≤ (𝐹𝑙) ↔ ∀𝑖𝑍𝑙 ∈ (ℤ𝑖)𝑥 ≤ (𝐹𝑙)))
10 fveq2 6839 . . . . . . . . . . 11 (𝑖 = 𝑘 → (ℤ𝑖) = (ℤ𝑘))
1110rexeqdv 3312 . . . . . . . . . 10 (𝑖 = 𝑘 → (∃𝑙 ∈ (ℤ𝑖)𝑥 ≤ (𝐹𝑙) ↔ ∃𝑙 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑙)))
12 nfcv 2905 . . . . . . . . . . . . 13 𝑗𝑥
13 nfcv 2905 . . . . . . . . . . . . 13 𝑗
14 limsupreuz.1 . . . . . . . . . . . . . 14 𝑗𝐹
15 nfcv 2905 . . . . . . . . . . . . . 14 𝑗𝑙
1614, 15nffv 6849 . . . . . . . . . . . . 13 𝑗(𝐹𝑙)
1712, 13, 16nfbr 5150 . . . . . . . . . . . 12 𝑗 𝑥 ≤ (𝐹𝑙)
18 nfv 1917 . . . . . . . . . . . 12 𝑙 𝑥 ≤ (𝐹𝑗)
19 fveq2 6839 . . . . . . . . . . . . 13 (𝑙 = 𝑗 → (𝐹𝑙) = (𝐹𝑗))
2019breq2d 5115 . . . . . . . . . . . 12 (𝑙 = 𝑗 → (𝑥 ≤ (𝐹𝑙) ↔ 𝑥 ≤ (𝐹𝑗)))
2117, 18, 20cbvrexw 3288 . . . . . . . . . . 11 (∃𝑙 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑙) ↔ ∃𝑗 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑗))
2221a1i 11 . . . . . . . . . 10 (𝑖 = 𝑘 → (∃𝑙 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑙) ↔ ∃𝑗 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑗)))
2311, 22bitrd 278 . . . . . . . . 9 (𝑖 = 𝑘 → (∃𝑙 ∈ (ℤ𝑖)𝑥 ≤ (𝐹𝑙) ↔ ∃𝑗 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑗)))
2423cbvralvw 3223 . . . . . . . 8 (∀𝑖𝑍𝑙 ∈ (ℤ𝑖)𝑥 ≤ (𝐹𝑙) ↔ ∀𝑘𝑍𝑗 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑗))
2524a1i 11 . . . . . . 7 (𝑦 = 𝑥 → (∀𝑖𝑍𝑙 ∈ (ℤ𝑖)𝑥 ≤ (𝐹𝑙) ↔ ∀𝑘𝑍𝑗 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑗)))
269, 25bitrd 278 . . . . . 6 (𝑦 = 𝑥 → (∀𝑖𝑍𝑙 ∈ (ℤ𝑖)𝑦 ≤ (𝐹𝑙) ↔ ∀𝑘𝑍𝑗 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑗)))
2726cbvrexvw 3224 . . . . 5 (∃𝑦 ∈ ℝ ∀𝑖𝑍𝑙 ∈ (ℤ𝑖)𝑦 ≤ (𝐹𝑙) ↔ ∃𝑥 ∈ ℝ ∀𝑘𝑍𝑗 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑗))
28 breq2 5107 . . . . . . . . 9 (𝑦 = 𝑥 → ((𝐹𝑙) ≤ 𝑦 ↔ (𝐹𝑙) ≤ 𝑥))
2928ralbidv 3172 . . . . . . . 8 (𝑦 = 𝑥 → (∀𝑙 ∈ (ℤ𝑖)(𝐹𝑙) ≤ 𝑦 ↔ ∀𝑙 ∈ (ℤ𝑖)(𝐹𝑙) ≤ 𝑥))
3029rexbidv 3173 . . . . . . 7 (𝑦 = 𝑥 → (∃𝑖𝑍𝑙 ∈ (ℤ𝑖)(𝐹𝑙) ≤ 𝑦 ↔ ∃𝑖𝑍𝑙 ∈ (ℤ𝑖)(𝐹𝑙) ≤ 𝑥))
3110raleqdv 3311 . . . . . . . . . 10 (𝑖 = 𝑘 → (∀𝑙 ∈ (ℤ𝑖)(𝐹𝑙) ≤ 𝑥 ↔ ∀𝑙 ∈ (ℤ𝑘)(𝐹𝑙) ≤ 𝑥))
3216, 13, 12nfbr 5150 . . . . . . . . . . . 12 𝑗(𝐹𝑙) ≤ 𝑥
33 nfv 1917 . . . . . . . . . . . 12 𝑙(𝐹𝑗) ≤ 𝑥
3419breq1d 5113 . . . . . . . . . . . 12 (𝑙 = 𝑗 → ((𝐹𝑙) ≤ 𝑥 ↔ (𝐹𝑗) ≤ 𝑥))
3532, 33, 34cbvralw 3287 . . . . . . . . . . 11 (∀𝑙 ∈ (ℤ𝑘)(𝐹𝑙) ≤ 𝑥 ↔ ∀𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥)
3635a1i 11 . . . . . . . . . 10 (𝑖 = 𝑘 → (∀𝑙 ∈ (ℤ𝑘)(𝐹𝑙) ≤ 𝑥 ↔ ∀𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥))
3731, 36bitrd 278 . . . . . . . . 9 (𝑖 = 𝑘 → (∀𝑙 ∈ (ℤ𝑖)(𝐹𝑙) ≤ 𝑥 ↔ ∀𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥))
3837cbvrexvw 3224 . . . . . . . 8 (∃𝑖𝑍𝑙 ∈ (ℤ𝑖)(𝐹𝑙) ≤ 𝑥 ↔ ∃𝑘𝑍𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥)
3938a1i 11 . . . . . . 7 (𝑦 = 𝑥 → (∃𝑖𝑍𝑙 ∈ (ℤ𝑖)(𝐹𝑙) ≤ 𝑥 ↔ ∃𝑘𝑍𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥))
4030, 39bitrd 278 . . . . . 6 (𝑦 = 𝑥 → (∃𝑖𝑍𝑙 ∈ (ℤ𝑖)(𝐹𝑙) ≤ 𝑦 ↔ ∃𝑘𝑍𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥))
4140cbvrexvw 3224 . . . . 5 (∃𝑦 ∈ ℝ ∃𝑖𝑍𝑙 ∈ (ℤ𝑖)(𝐹𝑙) ≤ 𝑦 ↔ ∃𝑥 ∈ ℝ ∃𝑘𝑍𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥)
4227, 41anbi12i 627 . . . 4 ((∃𝑦 ∈ ℝ ∀𝑖𝑍𝑙 ∈ (ℤ𝑖)𝑦 ≤ (𝐹𝑙) ∧ ∃𝑦 ∈ ℝ ∃𝑖𝑍𝑙 ∈ (ℤ𝑖)(𝐹𝑙) ≤ 𝑦) ↔ (∃𝑥 ∈ ℝ ∀𝑘𝑍𝑗 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑗) ∧ ∃𝑥 ∈ ℝ ∃𝑘𝑍𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥))
4342a1i 11 . . 3 (𝜑 → ((∃𝑦 ∈ ℝ ∀𝑖𝑍𝑙 ∈ (ℤ𝑖)𝑦 ≤ (𝐹𝑙) ∧ ∃𝑦 ∈ ℝ ∃𝑖𝑍𝑙 ∈ (ℤ𝑖)(𝐹𝑙) ≤ 𝑦) ↔ (∃𝑥 ∈ ℝ ∀𝑘𝑍𝑗 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑗) ∧ ∃𝑥 ∈ ℝ ∃𝑘𝑍𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥)))
446, 43bitrd 278 . 2 (𝜑 → ((lim sup‘𝐹) ∈ ℝ ↔ (∃𝑥 ∈ ℝ ∀𝑘𝑍𝑗 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑗) ∧ ∃𝑥 ∈ ℝ ∃𝑘𝑍𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥)))
45 nfv 1917 . . . . . . . 8 𝑖(𝐹𝑗) ≤ 𝑥
46 nfcv 2905 . . . . . . . . . 10 𝑗𝑖
4714, 46nffv 6849 . . . . . . . . 9 𝑗(𝐹𝑖)
4847, 13, 12nfbr 5150 . . . . . . . 8 𝑗(𝐹𝑖) ≤ 𝑥
49 fveq2 6839 . . . . . . . . 9 (𝑗 = 𝑖 → (𝐹𝑗) = (𝐹𝑖))
5049breq1d 5113 . . . . . . . 8 (𝑗 = 𝑖 → ((𝐹𝑗) ≤ 𝑥 ↔ (𝐹𝑖) ≤ 𝑥))
5145, 48, 50cbvralw 3287 . . . . . . 7 (∀𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥 ↔ ∀𝑖 ∈ (ℤ𝑘)(𝐹𝑖) ≤ 𝑥)
5251rexbii 3095 . . . . . 6 (∃𝑘𝑍𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥 ↔ ∃𝑘𝑍𝑖 ∈ (ℤ𝑘)(𝐹𝑖) ≤ 𝑥)
5352rexbii 3095 . . . . 5 (∃𝑥 ∈ ℝ ∃𝑘𝑍𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥 ↔ ∃𝑥 ∈ ℝ ∃𝑘𝑍𝑖 ∈ (ℤ𝑘)(𝐹𝑖) ≤ 𝑥)
5453a1i 11 . . . 4 (𝜑 → (∃𝑥 ∈ ℝ ∃𝑘𝑍𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥 ↔ ∃𝑥 ∈ ℝ ∃𝑘𝑍𝑖 ∈ (ℤ𝑘)(𝐹𝑖) ≤ 𝑥))
55 nfv 1917 . . . . 5 𝑖𝜑
564adantr 481 . . . . . 6 ((𝜑𝑖𝑍) → 𝐹:𝑍⟶ℝ)
57 simpr 485 . . . . . 6 ((𝜑𝑖𝑍) → 𝑖𝑍)
5856, 57ffvelcdmd 7032 . . . . 5 ((𝜑𝑖𝑍) → (𝐹𝑖) ∈ ℝ)
5955, 2, 3, 58uzub 43571 . . . 4 (𝜑 → (∃𝑥 ∈ ℝ ∃𝑘𝑍𝑖 ∈ (ℤ𝑘)(𝐹𝑖) ≤ 𝑥 ↔ ∃𝑥 ∈ ℝ ∀𝑖𝑍 (𝐹𝑖) ≤ 𝑥))
60 eqcom 2744 . . . . . . . . . 10 (𝑗 = 𝑖𝑖 = 𝑗)
6160imbi1i 349 . . . . . . . . 9 ((𝑗 = 𝑖 → ((𝐹𝑗) ≤ 𝑥 ↔ (𝐹𝑖) ≤ 𝑥)) ↔ (𝑖 = 𝑗 → ((𝐹𝑗) ≤ 𝑥 ↔ (𝐹𝑖) ≤ 𝑥)))
62 bicom 221 . . . . . . . . . 10 (((𝐹𝑗) ≤ 𝑥 ↔ (𝐹𝑖) ≤ 𝑥) ↔ ((𝐹𝑖) ≤ 𝑥 ↔ (𝐹𝑗) ≤ 𝑥))
6362imbi2i 335 . . . . . . . . 9 ((𝑖 = 𝑗 → ((𝐹𝑗) ≤ 𝑥 ↔ (𝐹𝑖) ≤ 𝑥)) ↔ (𝑖 = 𝑗 → ((𝐹𝑖) ≤ 𝑥 ↔ (𝐹𝑗) ≤ 𝑥)))
6461, 63bitri 274 . . . . . . . 8 ((𝑗 = 𝑖 → ((𝐹𝑗) ≤ 𝑥 ↔ (𝐹𝑖) ≤ 𝑥)) ↔ (𝑖 = 𝑗 → ((𝐹𝑖) ≤ 𝑥 ↔ (𝐹𝑗) ≤ 𝑥)))
6550, 64mpbi 229 . . . . . . 7 (𝑖 = 𝑗 → ((𝐹𝑖) ≤ 𝑥 ↔ (𝐹𝑗) ≤ 𝑥))
6648, 45, 65cbvralw 3287 . . . . . 6 (∀𝑖𝑍 (𝐹𝑖) ≤ 𝑥 ↔ ∀𝑗𝑍 (𝐹𝑗) ≤ 𝑥)
6766rexbii 3095 . . . . 5 (∃𝑥 ∈ ℝ ∀𝑖𝑍 (𝐹𝑖) ≤ 𝑥 ↔ ∃𝑥 ∈ ℝ ∀𝑗𝑍 (𝐹𝑗) ≤ 𝑥)
6867a1i 11 . . . 4 (𝜑 → (∃𝑥 ∈ ℝ ∀𝑖𝑍 (𝐹𝑖) ≤ 𝑥 ↔ ∃𝑥 ∈ ℝ ∀𝑗𝑍 (𝐹𝑗) ≤ 𝑥))
6954, 59, 683bitrd 304 . . 3 (𝜑 → (∃𝑥 ∈ ℝ ∃𝑘𝑍𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥 ↔ ∃𝑥 ∈ ℝ ∀𝑗𝑍 (𝐹𝑗) ≤ 𝑥))
7069anbi2d 629 . 2 (𝜑 → ((∃𝑥 ∈ ℝ ∀𝑘𝑍𝑗 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑗) ∧ ∃𝑥 ∈ ℝ ∃𝑘𝑍𝑗 ∈ (ℤ𝑘)(𝐹𝑗) ≤ 𝑥) ↔ (∃𝑥 ∈ ℝ ∀𝑘𝑍𝑗 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑗) ∧ ∃𝑥 ∈ ℝ ∀𝑗𝑍 (𝐹𝑗) ≤ 𝑥)))
7144, 70bitrd 278 1 (𝜑 → ((lim sup‘𝐹) ∈ ℝ ↔ (∃𝑥 ∈ ℝ ∀𝑘𝑍𝑗 ∈ (ℤ𝑘)𝑥 ≤ (𝐹𝑗) ∧ ∃𝑥 ∈ ℝ ∀𝑗𝑍 (𝐹𝑗) ≤ 𝑥)))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 205  wa 396   = wceq 1541  wcel 2106  wnfc 2885  wral 3062  wrex 3071   class class class wbr 5103  wf 6489  cfv 6493  cr 11008  cle 11148  cz 12457  cuz 12721  lim supclsp 15312
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-10 2137  ax-11 2154  ax-12 2171  ax-ext 2708  ax-rep 5240  ax-sep 5254  ax-nul 5261  ax-pow 5318  ax-pr 5382  ax-un 7664  ax-cnex 11065  ax-resscn 11066  ax-1cn 11067  ax-icn 11068  ax-addcl 11069  ax-addrcl 11070  ax-mulcl 11071  ax-mulrcl 11072  ax-mulcom 11073  ax-addass 11074  ax-mulass 11075  ax-distr 11076  ax-i2m1 11077  ax-1ne0 11078  ax-1rid 11079  ax-rnegex 11080  ax-rrecex 11081  ax-cnre 11082  ax-pre-lttri 11083  ax-pre-lttrn 11084  ax-pre-ltadd 11085  ax-pre-mulgt0 11086  ax-pre-sup 11087
This theorem depends on definitions:  df-bi 206  df-an 397  df-or 846  df-3or 1088  df-3an 1089  df-tru 1544  df-fal 1554  df-ex 1782  df-nf 1786  df-sb 2068  df-mo 2539  df-eu 2568  df-clab 2715  df-cleq 2729  df-clel 2815  df-nfc 2887  df-ne 2942  df-nel 3048  df-ral 3063  df-rex 3072  df-rmo 3351  df-reu 3352  df-rab 3406  df-v 3445  df-sbc 3738  df-csb 3854  df-dif 3911  df-un 3913  df-in 3915  df-ss 3925  df-pss 3927  df-nul 4281  df-if 4485  df-pw 4560  df-sn 4585  df-pr 4587  df-op 4591  df-uni 4864  df-iun 4954  df-br 5104  df-opab 5166  df-mpt 5187  df-tr 5221  df-id 5529  df-eprel 5535  df-po 5543  df-so 5544  df-fr 5586  df-we 5588  df-xp 5637  df-rel 5638  df-cnv 5639  df-co 5640  df-dm 5641  df-rn 5642  df-res 5643  df-ima 5644  df-pred 6251  df-ord 6318  df-on 6319  df-lim 6320  df-suc 6321  df-iota 6445  df-fun 6495  df-fn 6496  df-f 6497  df-f1 6498  df-fo 6499  df-f1o 6500  df-fv 6501  df-riota 7307  df-ov 7354  df-oprab 7355  df-mpo 7356  df-om 7795  df-1st 7913  df-2nd 7914  df-frecs 8204  df-wrecs 8235  df-recs 8309  df-rdg 8348  df-1o 8404  df-er 8606  df-en 8842  df-dom 8843  df-sdom 8844  df-fin 8845  df-sup 9336  df-inf 9337  df-pnf 11149  df-mnf 11150  df-xr 11151  df-ltxr 11152  df-le 11153  df-sub 11345  df-neg 11346  df-nn 12112  df-n0 12372  df-z 12458  df-uz 12722  df-ico 13224  df-fz 13379  df-fzo 13522  df-fl 13651  df-ceil 13652  df-limsup 15313
This theorem is referenced by:  limsupreuzmpt  43881  limsupgtlem  43919
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