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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 14610. This is a representation of .111... in binary with an infinite number of 1's. Theorem 0.999... 14612 proves a similar claim for .999... in base 10. (Contributed by David A. Wheeler, 4-Jan-2017.) |
Ref | Expression |
---|---|
geoihalfsum | ⊢ Σ𝑘 ∈ ℕ (1 / (2↑𝑘)) = 1 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 2cn 11091 | . . . . 5 ⊢ 2 ∈ ℂ | |
2 | 1 | a1i 11 | . . . 4 ⊢ (𝑘 ∈ ℕ → 2 ∈ ℂ) |
3 | 2ne0 11113 | . . . . 5 ⊢ 2 ≠ 0 | |
4 | 3 | a1i 11 | . . . 4 ⊢ (𝑘 ∈ ℕ → 2 ≠ 0) |
5 | nnz 11399 | . . . 4 ⊢ (𝑘 ∈ ℕ → 𝑘 ∈ ℤ) | |
6 | 2, 4, 5 | exprecd 13016 | . . 3 ⊢ (𝑘 ∈ ℕ → ((1 / 2)↑𝑘) = (1 / (2↑𝑘))) |
7 | 6 | sumeq2i 14429 | . 2 ⊢ Σ𝑘 ∈ ℕ ((1 / 2)↑𝑘) = Σ𝑘 ∈ ℕ (1 / (2↑𝑘)) |
8 | halfcn 11247 | . . . 4 ⊢ (1 / 2) ∈ ℂ | |
9 | halfre 11246 | . . . . . 6 ⊢ (1 / 2) ∈ ℝ | |
10 | 0le1 10551 | . . . . . . 7 ⊢ 0 ≤ 1 | |
11 | 1re 10039 | . . . . . . . 8 ⊢ 1 ∈ ℝ | |
12 | 2re 11090 | . . . . . . . 8 ⊢ 2 ∈ ℝ | |
13 | 2pos 11112 | . . . . . . . 8 ⊢ 0 < 2 | |
14 | ge0div 10890 | . . . . . . . 8 ⊢ ((1 ∈ ℝ ∧ 2 ∈ ℝ ∧ 0 < 2) → (0 ≤ 1 ↔ 0 ≤ (1 / 2))) | |
15 | 11, 12, 13, 14 | mp3an 1424 | . . . . . . 7 ⊢ (0 ≤ 1 ↔ 0 ≤ (1 / 2)) |
16 | 10, 15 | mpbi 220 | . . . . . 6 ⊢ 0 ≤ (1 / 2) |
17 | absid 14036 | . . . . . 6 ⊢ (((1 / 2) ∈ ℝ ∧ 0 ≤ (1 / 2)) → (abs‘(1 / 2)) = (1 / 2)) | |
18 | 9, 16, 17 | mp2an 708 | . . . . 5 ⊢ (abs‘(1 / 2)) = (1 / 2) |
19 | halflt1 11250 | . . . . 5 ⊢ (1 / 2) < 1 | |
20 | 18, 19 | eqbrtri 4674 | . . . 4 ⊢ (abs‘(1 / 2)) < 1 |
21 | geoisum1 14610 | . . . 4 ⊢ (((1 / 2) ∈ ℂ ∧ (abs‘(1 / 2)) < 1) → Σ𝑘 ∈ ℕ ((1 / 2)↑𝑘) = ((1 / 2) / (1 − (1 / 2)))) | |
22 | 8, 20, 21 | mp2an 708 | . . 3 ⊢ Σ𝑘 ∈ ℕ ((1 / 2)↑𝑘) = ((1 / 2) / (1 − (1 / 2))) |
23 | 1mhlfehlf 11251 | . . . 4 ⊢ (1 − (1 / 2)) = (1 / 2) | |
24 | 23 | oveq2i 6661 | . . 3 ⊢ ((1 / 2) / (1 − (1 / 2))) = ((1 / 2) / (1 / 2)) |
25 | ax-1cn 9994 | . . . . 5 ⊢ 1 ∈ ℂ | |
26 | ax-1ne0 10005 | . . . . 5 ⊢ 1 ≠ 0 | |
27 | 25, 1, 26, 3 | divne0i 10773 | . . . 4 ⊢ (1 / 2) ≠ 0 |
28 | 8, 27 | dividi 10758 | . . 3 ⊢ ((1 / 2) / (1 / 2)) = 1 |
29 | 22, 24, 28 | 3eqtri 2648 | . 2 ⊢ Σ𝑘 ∈ ℕ ((1 / 2)↑𝑘) = 1 |
30 | 7, 29 | eqtr3i 2646 | 1 ⊢ Σ𝑘 ∈ ℕ (1 / (2↑𝑘)) = 1 |
Colors of variables: wff setvar class |
Syntax hints: ↔ wb 196 = wceq 1483 ∈ wcel 1990 ≠ wne 2794 class class class wbr 4653 ‘cfv 5888 (class class class)co 6650 ℂcc 9934 ℝcr 9935 0cc0 9936 1c1 9937 < clt 10074 ≤ cle 10075 − cmin 10266 / cdiv 10684 ℕcn 11020 2c2 11070 ↑cexp 12860 abscabs 13974 Σcsu 14416 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1722 ax-4 1737 ax-5 1839 ax-6 1888 ax-7 1935 ax-8 1992 ax-9 1999 ax-10 2019 ax-11 2034 ax-12 2047 ax-13 2246 ax-ext 2602 ax-rep 4771 ax-sep 4781 ax-nul 4789 ax-pow 4843 ax-pr 4906 ax-un 6949 ax-inf2 8538 ax-cnex 9992 ax-resscn 9993 ax-1cn 9994 ax-icn 9995 ax-addcl 9996 ax-addrcl 9997 ax-mulcl 9998 ax-mulrcl 9999 ax-mulcom 10000 ax-addass 10001 ax-mulass 10002 ax-distr 10003 ax-i2m1 10004 ax-1ne0 10005 ax-1rid 10006 ax-rnegex 10007 ax-rrecex 10008 ax-cnre 10009 ax-pre-lttri 10010 ax-pre-lttrn 10011 ax-pre-ltadd 10012 ax-pre-mulgt0 10013 ax-pre-sup 10014 |
This theorem depends on definitions: df-bi 197 df-or 385 df-an 386 df-3or 1038 df-3an 1039 df-tru 1486 df-fal 1489 df-ex 1705 df-nf 1710 df-sb 1881 df-eu 2474 df-mo 2475 df-clab 2609 df-cleq 2615 df-clel 2618 df-nfc 2753 df-ne 2795 df-nel 2898 df-ral 2917 df-rex 2918 df-reu 2919 df-rmo 2920 df-rab 2921 df-v 3202 df-sbc 3436 df-csb 3534 df-dif 3577 df-un 3579 df-in 3581 df-ss 3588 df-pss 3590 df-nul 3916 df-if 4087 df-pw 4160 df-sn 4178 df-pr 4180 df-tp 4182 df-op 4184 df-uni 4437 df-int 4476 df-iun 4522 df-br 4654 df-opab 4713 df-mpt 4730 df-tr 4753 df-id 5024 df-eprel 5029 df-po 5035 df-so 5036 df-fr 5073 df-se 5074 df-we 5075 df-xp 5120 df-rel 5121 df-cnv 5122 df-co 5123 df-dm 5124 df-rn 5125 df-res 5126 df-ima 5127 df-pred 5680 df-ord 5726 df-on 5727 df-lim 5728 df-suc 5729 df-iota 5851 df-fun 5890 df-fn 5891 df-f 5892 df-f1 5893 df-fo 5894 df-f1o 5895 df-fv 5896 df-isom 5897 df-riota 6611 df-ov 6653 df-oprab 6654 df-mpt2 6655 df-om 7066 df-1st 7168 df-2nd 7169 df-wrecs 7407 df-recs 7468 df-rdg 7506 df-1o 7560 df-oadd 7564 df-er 7742 df-pm 7860 df-en 7956 df-dom 7957 df-sdom 7958 df-fin 7959 df-sup 8348 df-inf 8349 df-oi 8415 df-card 8765 df-pnf 10076 df-mnf 10077 df-xr 10078 df-ltxr 10079 df-le 10080 df-sub 10268 df-neg 10269 df-div 10685 df-nn 11021 df-2 11079 df-3 11080 df-n0 11293 df-z 11378 df-uz 11688 df-rp 11833 df-fz 12327 df-fzo 12466 df-fl 12593 df-seq 12802 df-exp 12861 df-hash 13118 df-cj 13839 df-re 13840 df-im 13841 df-sqrt 13975 df-abs 13976 df-clim 14219 df-rlim 14220 df-sum 14417 |
This theorem is referenced by: omssubadd 30362 |
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