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Mirrors > Home > MPE Home > Th. List > geoihalfsum | Structured version Visualization version GIF version |
Description: Prove that the infinite geometric series of 1/2, 1/2 + 1/4 + 1/8 + ... = 1. Uses geoisum1 15911. This is a representation of .111... in binary with an infinite number of 1's. Theorem 0.999... 15913 proves a similar claim for .999... in base 10. (Contributed by David A. Wheeler, 4-Jan-2017.) (Proof shortened by AV, 9-Jul-2022.) |
Ref | Expression |
---|---|
geoihalfsum | ⊢ Σ𝑘 ∈ ℕ (1 / (2↑𝑘)) = 1 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 2cn 12338 | . . . . 5 ⊢ 2 ∈ ℂ | |
2 | 1 | a1i 11 | . . . 4 ⊢ (𝑘 ∈ ℕ → 2 ∈ ℂ) |
3 | 2ne0 12367 | . . . . 5 ⊢ 2 ≠ 0 | |
4 | 3 | a1i 11 | . . . 4 ⊢ (𝑘 ∈ ℕ → 2 ≠ 0) |
5 | nnz 12631 | . . . 4 ⊢ (𝑘 ∈ ℕ → 𝑘 ∈ ℤ) | |
6 | 2, 4, 5 | exprecd 14190 | . . 3 ⊢ (𝑘 ∈ ℕ → ((1 / 2)↑𝑘) = (1 / (2↑𝑘))) |
7 | 6 | sumeq2i 15730 | . 2 ⊢ Σ𝑘 ∈ ℕ ((1 / 2)↑𝑘) = Σ𝑘 ∈ ℕ (1 / (2↑𝑘)) |
8 | halfcn 12478 | . . . 4 ⊢ (1 / 2) ∈ ℂ | |
9 | halfre 12477 | . . . . . 6 ⊢ (1 / 2) ∈ ℝ | |
10 | halfge0 12480 | . . . . . 6 ⊢ 0 ≤ (1 / 2) | |
11 | absid 15331 | . . . . . 6 ⊢ (((1 / 2) ∈ ℝ ∧ 0 ≤ (1 / 2)) → (abs‘(1 / 2)) = (1 / 2)) | |
12 | 9, 10, 11 | mp2an 692 | . . . . 5 ⊢ (abs‘(1 / 2)) = (1 / 2) |
13 | halflt1 12481 | . . . . 5 ⊢ (1 / 2) < 1 | |
14 | 12, 13 | eqbrtri 5168 | . . . 4 ⊢ (abs‘(1 / 2)) < 1 |
15 | geoisum1 15911 | . . . 4 ⊢ (((1 / 2) ∈ ℂ ∧ (abs‘(1 / 2)) < 1) → Σ𝑘 ∈ ℕ ((1 / 2)↑𝑘) = ((1 / 2) / (1 − (1 / 2)))) | |
16 | 8, 14, 15 | mp2an 692 | . . 3 ⊢ Σ𝑘 ∈ ℕ ((1 / 2)↑𝑘) = ((1 / 2) / (1 − (1 / 2))) |
17 | 1mhlfehlf 12482 | . . . 4 ⊢ (1 − (1 / 2)) = (1 / 2) | |
18 | 17 | oveq2i 7441 | . . 3 ⊢ ((1 / 2) / (1 − (1 / 2))) = ((1 / 2) / (1 / 2)) |
19 | ax-1cn 11210 | . . . . 5 ⊢ 1 ∈ ℂ | |
20 | ax-1ne0 11221 | . . . . 5 ⊢ 1 ≠ 0 | |
21 | 19, 1, 20, 3 | divne0i 12012 | . . . 4 ⊢ (1 / 2) ≠ 0 |
22 | 8, 21 | dividi 11997 | . . 3 ⊢ ((1 / 2) / (1 / 2)) = 1 |
23 | 16, 18, 22 | 3eqtri 2766 | . 2 ⊢ Σ𝑘 ∈ ℕ ((1 / 2)↑𝑘) = 1 |
24 | 7, 23 | eqtr3i 2764 | 1 ⊢ Σ𝑘 ∈ ℕ (1 / (2↑𝑘)) = 1 |
Colors of variables: wff setvar class |
Syntax hints: = wceq 1536 ∈ wcel 2105 ≠ wne 2937 class class class wbr 5147 ‘cfv 6562 (class class class)co 7430 ℂcc 11150 ℝcr 11151 0cc0 11152 1c1 11153 < clt 11292 ≤ cle 11293 − cmin 11489 / cdiv 11917 ℕcn 12263 2c2 12318 ↑cexp 14098 abscabs 15269 Σcsu 15718 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1791 ax-4 1805 ax-5 1907 ax-6 1964 ax-7 2004 ax-8 2107 ax-9 2115 ax-10 2138 ax-11 2154 ax-12 2174 ax-ext 2705 ax-rep 5284 ax-sep 5301 ax-nul 5311 ax-pow 5370 ax-pr 5437 ax-un 7753 ax-inf2 9678 ax-cnex 11208 ax-resscn 11209 ax-1cn 11210 ax-icn 11211 ax-addcl 11212 ax-addrcl 11213 ax-mulcl 11214 ax-mulrcl 11215 ax-mulcom 11216 ax-addass 11217 ax-mulass 11218 ax-distr 11219 ax-i2m1 11220 ax-1ne0 11221 ax-1rid 11222 ax-rnegex 11223 ax-rrecex 11224 ax-cnre 11225 ax-pre-lttri 11226 ax-pre-lttrn 11227 ax-pre-ltadd 11228 ax-pre-mulgt0 11229 ax-pre-sup 11230 |
This theorem depends on definitions: df-bi 207 df-an 396 df-or 848 df-3or 1087 df-3an 1088 df-tru 1539 df-fal 1549 df-ex 1776 df-nf 1780 df-sb 2062 df-mo 2537 df-eu 2566 df-clab 2712 df-cleq 2726 df-clel 2813 df-nfc 2889 df-ne 2938 df-nel 3044 df-ral 3059 df-rex 3068 df-rmo 3377 df-reu 3378 df-rab 3433 df-v 3479 df-sbc 3791 df-csb 3908 df-dif 3965 df-un 3967 df-in 3969 df-ss 3979 df-pss 3982 df-nul 4339 df-if 4531 df-pw 4606 df-sn 4631 df-pr 4633 df-op 4637 df-uni 4912 df-int 4951 df-iun 4997 df-br 5148 df-opab 5210 df-mpt 5231 df-tr 5265 df-id 5582 df-eprel 5588 df-po 5596 df-so 5597 df-fr 5640 df-se 5641 df-we 5642 df-xp 5694 df-rel 5695 df-cnv 5696 df-co 5697 df-dm 5698 df-rn 5699 df-res 5700 df-ima 5701 df-pred 6322 df-ord 6388 df-on 6389 df-lim 6390 df-suc 6391 df-iota 6515 df-fun 6564 df-fn 6565 df-f 6566 df-f1 6567 df-fo 6568 df-f1o 6569 df-fv 6570 df-isom 6571 df-riota 7387 df-ov 7433 df-oprab 7434 df-mpo 7435 df-om 7887 df-1st 8012 df-2nd 8013 df-frecs 8304 df-wrecs 8335 df-recs 8409 df-rdg 8448 df-1o 8504 df-er 8743 df-pm 8867 df-en 8984 df-dom 8985 df-sdom 8986 df-fin 8987 df-sup 9479 df-inf 9480 df-oi 9547 df-card 9976 df-pnf 11294 df-mnf 11295 df-xr 11296 df-ltxr 11297 df-le 11298 df-sub 11491 df-neg 11492 df-div 11918 df-nn 12264 df-2 12326 df-3 12327 df-n0 12524 df-z 12611 df-uz 12876 df-rp 13032 df-fz 13544 df-fzo 13691 df-fl 13828 df-seq 14039 df-exp 14099 df-hash 14366 df-cj 15134 df-re 15135 df-im 15136 df-sqrt 15270 df-abs 15271 df-clim 15520 df-rlim 15521 df-sum 15719 |
This theorem is referenced by: omssubadd 34281 |
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