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Mirrors > Home > ILE Home > Th. List > expnlbnd | GIF version |
Description: The reciprocal of exponentiation with a base greater than 1 has no positive lower bound. (Contributed by NM, 18-Jul-2008.) |
Ref | Expression |
---|---|
expnlbnd | ⊢ ((𝐴 ∈ ℝ+ ∧ 𝐵 ∈ ℝ ∧ 1 < 𝐵) → ∃𝑘 ∈ ℕ (1 / (𝐵↑𝑘)) < 𝐴) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | rpre 9590 | . . . 4 ⊢ (𝐴 ∈ ℝ+ → 𝐴 ∈ ℝ) | |
2 | rpap0 9600 | . . . 4 ⊢ (𝐴 ∈ ℝ+ → 𝐴 # 0) | |
3 | 1, 2 | rerecclapd 8724 | . . 3 ⊢ (𝐴 ∈ ℝ+ → (1 / 𝐴) ∈ ℝ) |
4 | expnbnd 10572 | . . 3 ⊢ (((1 / 𝐴) ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 1 < 𝐵) → ∃𝑘 ∈ ℕ (1 / 𝐴) < (𝐵↑𝑘)) | |
5 | 3, 4 | syl3an1 1260 | . 2 ⊢ ((𝐴 ∈ ℝ+ ∧ 𝐵 ∈ ℝ ∧ 1 < 𝐵) → ∃𝑘 ∈ ℕ (1 / 𝐴) < (𝐵↑𝑘)) |
6 | rpregt0 9597 | . . . . . 6 ⊢ (𝐴 ∈ ℝ+ → (𝐴 ∈ ℝ ∧ 0 < 𝐴)) | |
7 | 6 | 3ad2ant1 1007 | . . . . 5 ⊢ ((𝐴 ∈ ℝ+ ∧ 𝐵 ∈ ℝ ∧ 1 < 𝐵) → (𝐴 ∈ ℝ ∧ 0 < 𝐴)) |
8 | 7 | adantr 274 | . . . 4 ⊢ (((𝐴 ∈ ℝ+ ∧ 𝐵 ∈ ℝ ∧ 1 < 𝐵) ∧ 𝑘 ∈ ℕ) → (𝐴 ∈ ℝ ∧ 0 < 𝐴)) |
9 | nnnn0 9115 | . . . . . . . 8 ⊢ (𝑘 ∈ ℕ → 𝑘 ∈ ℕ0) | |
10 | reexpcl 10466 | . . . . . . . 8 ⊢ ((𝐵 ∈ ℝ ∧ 𝑘 ∈ ℕ0) → (𝐵↑𝑘) ∈ ℝ) | |
11 | 9, 10 | sylan2 284 | . . . . . . 7 ⊢ ((𝐵 ∈ ℝ ∧ 𝑘 ∈ ℕ) → (𝐵↑𝑘) ∈ ℝ) |
12 | 11 | adantlr 469 | . . . . . 6 ⊢ (((𝐵 ∈ ℝ ∧ 1 < 𝐵) ∧ 𝑘 ∈ ℕ) → (𝐵↑𝑘) ∈ ℝ) |
13 | simpll 519 | . . . . . . 7 ⊢ (((𝐵 ∈ ℝ ∧ 1 < 𝐵) ∧ 𝑘 ∈ ℕ) → 𝐵 ∈ ℝ) | |
14 | nnz 9204 | . . . . . . . 8 ⊢ (𝑘 ∈ ℕ → 𝑘 ∈ ℤ) | |
15 | 14 | adantl 275 | . . . . . . 7 ⊢ (((𝐵 ∈ ℝ ∧ 1 < 𝐵) ∧ 𝑘 ∈ ℕ) → 𝑘 ∈ ℤ) |
16 | 0lt1 8019 | . . . . . . . . . 10 ⊢ 0 < 1 | |
17 | 0re 7893 | . . . . . . . . . . 11 ⊢ 0 ∈ ℝ | |
18 | 1re 7892 | . . . . . . . . . . 11 ⊢ 1 ∈ ℝ | |
19 | lttr 7966 | . . . . . . . . . . 11 ⊢ ((0 ∈ ℝ ∧ 1 ∈ ℝ ∧ 𝐵 ∈ ℝ) → ((0 < 1 ∧ 1 < 𝐵) → 0 < 𝐵)) | |
20 | 17, 18, 19 | mp3an12 1316 | . . . . . . . . . 10 ⊢ (𝐵 ∈ ℝ → ((0 < 1 ∧ 1 < 𝐵) → 0 < 𝐵)) |
21 | 16, 20 | mpani 427 | . . . . . . . . 9 ⊢ (𝐵 ∈ ℝ → (1 < 𝐵 → 0 < 𝐵)) |
22 | 21 | imp 123 | . . . . . . . 8 ⊢ ((𝐵 ∈ ℝ ∧ 1 < 𝐵) → 0 < 𝐵) |
23 | 22 | adantr 274 | . . . . . . 7 ⊢ (((𝐵 ∈ ℝ ∧ 1 < 𝐵) ∧ 𝑘 ∈ ℕ) → 0 < 𝐵) |
24 | expgt0 10482 | . . . . . . 7 ⊢ ((𝐵 ∈ ℝ ∧ 𝑘 ∈ ℤ ∧ 0 < 𝐵) → 0 < (𝐵↑𝑘)) | |
25 | 13, 15, 23, 24 | syl3anc 1227 | . . . . . 6 ⊢ (((𝐵 ∈ ℝ ∧ 1 < 𝐵) ∧ 𝑘 ∈ ℕ) → 0 < (𝐵↑𝑘)) |
26 | 12, 25 | jca 304 | . . . . 5 ⊢ (((𝐵 ∈ ℝ ∧ 1 < 𝐵) ∧ 𝑘 ∈ ℕ) → ((𝐵↑𝑘) ∈ ℝ ∧ 0 < (𝐵↑𝑘))) |
27 | 26 | 3adantl1 1142 | . . . 4 ⊢ (((𝐴 ∈ ℝ+ ∧ 𝐵 ∈ ℝ ∧ 1 < 𝐵) ∧ 𝑘 ∈ ℕ) → ((𝐵↑𝑘) ∈ ℝ ∧ 0 < (𝐵↑𝑘))) |
28 | ltrec1 8777 | . . . 4 ⊢ (((𝐴 ∈ ℝ ∧ 0 < 𝐴) ∧ ((𝐵↑𝑘) ∈ ℝ ∧ 0 < (𝐵↑𝑘))) → ((1 / 𝐴) < (𝐵↑𝑘) ↔ (1 / (𝐵↑𝑘)) < 𝐴)) | |
29 | 8, 27, 28 | syl2anc 409 | . . 3 ⊢ (((𝐴 ∈ ℝ+ ∧ 𝐵 ∈ ℝ ∧ 1 < 𝐵) ∧ 𝑘 ∈ ℕ) → ((1 / 𝐴) < (𝐵↑𝑘) ↔ (1 / (𝐵↑𝑘)) < 𝐴)) |
30 | 29 | rexbidva 2461 | . 2 ⊢ ((𝐴 ∈ ℝ+ ∧ 𝐵 ∈ ℝ ∧ 1 < 𝐵) → (∃𝑘 ∈ ℕ (1 / 𝐴) < (𝐵↑𝑘) ↔ ∃𝑘 ∈ ℕ (1 / (𝐵↑𝑘)) < 𝐴)) |
31 | 5, 30 | mpbid 146 | 1 ⊢ ((𝐴 ∈ ℝ+ ∧ 𝐵 ∈ ℝ ∧ 1 < 𝐵) → ∃𝑘 ∈ ℕ (1 / (𝐵↑𝑘)) < 𝐴) |
Colors of variables: wff set class |
Syntax hints: → wi 4 ∧ wa 103 ↔ wb 104 ∧ w3a 967 ∈ wcel 2135 ∃wrex 2443 class class class wbr 3979 (class class class)co 5839 ℝcr 7746 0cc0 7747 1c1 7748 < clt 7927 / cdiv 8562 ℕcn 8851 ℕ0cn0 9108 ℤcz 9185 ℝ+crp 9583 ↑cexp 10448 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-in1 604 ax-in2 605 ax-io 699 ax-5 1434 ax-7 1435 ax-gen 1436 ax-ie1 1480 ax-ie2 1481 ax-8 1491 ax-10 1492 ax-11 1493 ax-i12 1494 ax-bndl 1496 ax-4 1497 ax-17 1513 ax-i9 1517 ax-ial 1521 ax-i5r 1522 ax-13 2137 ax-14 2138 ax-ext 2146 ax-coll 4094 ax-sep 4097 ax-nul 4105 ax-pow 4150 ax-pr 4184 ax-un 4408 ax-setind 4511 ax-iinf 4562 ax-cnex 7838 ax-resscn 7839 ax-1cn 7840 ax-1re 7841 ax-icn 7842 ax-addcl 7843 ax-addrcl 7844 ax-mulcl 7845 ax-mulrcl 7846 ax-addcom 7847 ax-mulcom 7848 ax-addass 7849 ax-mulass 7850 ax-distr 7851 ax-i2m1 7852 ax-0lt1 7853 ax-1rid 7854 ax-0id 7855 ax-rnegex 7856 ax-precex 7857 ax-cnre 7858 ax-pre-ltirr 7859 ax-pre-ltwlin 7860 ax-pre-lttrn 7861 ax-pre-apti 7862 ax-pre-ltadd 7863 ax-pre-mulgt0 7864 ax-pre-mulext 7865 ax-arch 7866 |
This theorem depends on definitions: df-bi 116 df-dc 825 df-3or 968 df-3an 969 df-tru 1345 df-fal 1348 df-nf 1448 df-sb 1750 df-eu 2016 df-mo 2017 df-clab 2151 df-cleq 2157 df-clel 2160 df-nfc 2295 df-ne 2335 df-nel 2430 df-ral 2447 df-rex 2448 df-reu 2449 df-rmo 2450 df-rab 2451 df-v 2726 df-sbc 2950 df-csb 3044 df-dif 3116 df-un 3118 df-in 3120 df-ss 3127 df-nul 3408 df-if 3519 df-pw 3558 df-sn 3579 df-pr 3580 df-op 3582 df-uni 3787 df-int 3822 df-iun 3865 df-br 3980 df-opab 4041 df-mpt 4042 df-tr 4078 df-id 4268 df-po 4271 df-iso 4272 df-iord 4341 df-on 4343 df-ilim 4344 df-suc 4346 df-iom 4565 df-xp 4607 df-rel 4608 df-cnv 4609 df-co 4610 df-dm 4611 df-rn 4612 df-res 4613 df-ima 4614 df-iota 5150 df-fun 5187 df-fn 5188 df-f 5189 df-f1 5190 df-fo 5191 df-f1o 5192 df-fv 5193 df-riota 5795 df-ov 5842 df-oprab 5843 df-mpo 5844 df-1st 6103 df-2nd 6104 df-recs 6267 df-frec 6353 df-pnf 7929 df-mnf 7930 df-xr 7931 df-ltxr 7932 df-le 7933 df-sub 8065 df-neg 8066 df-reap 8467 df-ap 8474 df-div 8563 df-inn 8852 df-n0 9109 df-z 9186 df-uz 9461 df-rp 9584 df-seqfrec 10375 df-exp 10449 |
This theorem is referenced by: expnlbnd2 10574 |
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