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Mirrors > Home > MPE Home > Th. List > rddif | Structured version Visualization version GIF version |
Description: The difference between a real number and its nearest integer is less than or equal to one half. (Contributed by Jeff Madsen, 2-Sep-2009.) (Proof shortened by Mario Carneiro, 14-Sep-2015.) |
Ref | Expression |
---|---|
rddif | ⊢ (𝐴 ∈ ℝ → (abs‘((⌊‘(𝐴 + (1 / 2))) − 𝐴)) ≤ (1 / 2)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | halfcn 11247 | . . . . . . . 8 ⊢ (1 / 2) ∈ ℂ | |
2 | 1 | 2timesi 11147 | . . . . . . 7 ⊢ (2 · (1 / 2)) = ((1 / 2) + (1 / 2)) |
3 | 2cn 11091 | . . . . . . . 8 ⊢ 2 ∈ ℂ | |
4 | 2ne0 11113 | . . . . . . . 8 ⊢ 2 ≠ 0 | |
5 | 3, 4 | recidi 10756 | . . . . . . 7 ⊢ (2 · (1 / 2)) = 1 |
6 | 2, 5 | eqtr3i 2646 | . . . . . 6 ⊢ ((1 / 2) + (1 / 2)) = 1 |
7 | 6 | oveq2i 6661 | . . . . 5 ⊢ ((𝐴 − (1 / 2)) + ((1 / 2) + (1 / 2))) = ((𝐴 − (1 / 2)) + 1) |
8 | recn 10026 | . . . . . 6 ⊢ (𝐴 ∈ ℝ → 𝐴 ∈ ℂ) | |
9 | 1 | a1i 11 | . . . . . 6 ⊢ (𝐴 ∈ ℝ → (1 / 2) ∈ ℂ) |
10 | 8, 9, 9 | nppcan3d 10419 | . . . . 5 ⊢ (𝐴 ∈ ℝ → ((𝐴 − (1 / 2)) + ((1 / 2) + (1 / 2))) = (𝐴 + (1 / 2))) |
11 | 7, 10 | syl5eqr 2670 | . . . 4 ⊢ (𝐴 ∈ ℝ → ((𝐴 − (1 / 2)) + 1) = (𝐴 + (1 / 2))) |
12 | halfre 11246 | . . . . . 6 ⊢ (1 / 2) ∈ ℝ | |
13 | readdcl 10019 | . . . . . 6 ⊢ ((𝐴 ∈ ℝ ∧ (1 / 2) ∈ ℝ) → (𝐴 + (1 / 2)) ∈ ℝ) | |
14 | 12, 13 | mpan2 707 | . . . . 5 ⊢ (𝐴 ∈ ℝ → (𝐴 + (1 / 2)) ∈ ℝ) |
15 | fllep1 12602 | . . . . 5 ⊢ ((𝐴 + (1 / 2)) ∈ ℝ → (𝐴 + (1 / 2)) ≤ ((⌊‘(𝐴 + (1 / 2))) + 1)) | |
16 | 14, 15 | syl 17 | . . . 4 ⊢ (𝐴 ∈ ℝ → (𝐴 + (1 / 2)) ≤ ((⌊‘(𝐴 + (1 / 2))) + 1)) |
17 | 11, 16 | eqbrtrd 4675 | . . 3 ⊢ (𝐴 ∈ ℝ → ((𝐴 − (1 / 2)) + 1) ≤ ((⌊‘(𝐴 + (1 / 2))) + 1)) |
18 | resubcl 10345 | . . . . 5 ⊢ ((𝐴 ∈ ℝ ∧ (1 / 2) ∈ ℝ) → (𝐴 − (1 / 2)) ∈ ℝ) | |
19 | 12, 18 | mpan2 707 | . . . 4 ⊢ (𝐴 ∈ ℝ → (𝐴 − (1 / 2)) ∈ ℝ) |
20 | reflcl 12597 | . . . . 5 ⊢ ((𝐴 + (1 / 2)) ∈ ℝ → (⌊‘(𝐴 + (1 / 2))) ∈ ℝ) | |
21 | 14, 20 | syl 17 | . . . 4 ⊢ (𝐴 ∈ ℝ → (⌊‘(𝐴 + (1 / 2))) ∈ ℝ) |
22 | 1red 10055 | . . . 4 ⊢ (𝐴 ∈ ℝ → 1 ∈ ℝ) | |
23 | 19, 21, 22 | leadd1d 10621 | . . 3 ⊢ (𝐴 ∈ ℝ → ((𝐴 − (1 / 2)) ≤ (⌊‘(𝐴 + (1 / 2))) ↔ ((𝐴 − (1 / 2)) + 1) ≤ ((⌊‘(𝐴 + (1 / 2))) + 1))) |
24 | 17, 23 | mpbird 247 | . 2 ⊢ (𝐴 ∈ ℝ → (𝐴 − (1 / 2)) ≤ (⌊‘(𝐴 + (1 / 2)))) |
25 | flle 12600 | . . 3 ⊢ ((𝐴 + (1 / 2)) ∈ ℝ → (⌊‘(𝐴 + (1 / 2))) ≤ (𝐴 + (1 / 2))) | |
26 | 14, 25 | syl 17 | . 2 ⊢ (𝐴 ∈ ℝ → (⌊‘(𝐴 + (1 / 2))) ≤ (𝐴 + (1 / 2))) |
27 | id 22 | . . 3 ⊢ (𝐴 ∈ ℝ → 𝐴 ∈ ℝ) | |
28 | 12 | a1i 11 | . . 3 ⊢ (𝐴 ∈ ℝ → (1 / 2) ∈ ℝ) |
29 | absdifle 14058 | . . 3 ⊢ (((⌊‘(𝐴 + (1 / 2))) ∈ ℝ ∧ 𝐴 ∈ ℝ ∧ (1 / 2) ∈ ℝ) → ((abs‘((⌊‘(𝐴 + (1 / 2))) − 𝐴)) ≤ (1 / 2) ↔ ((𝐴 − (1 / 2)) ≤ (⌊‘(𝐴 + (1 / 2))) ∧ (⌊‘(𝐴 + (1 / 2))) ≤ (𝐴 + (1 / 2))))) | |
30 | 21, 27, 28, 29 | syl3anc 1326 | . 2 ⊢ (𝐴 ∈ ℝ → ((abs‘((⌊‘(𝐴 + (1 / 2))) − 𝐴)) ≤ (1 / 2) ↔ ((𝐴 − (1 / 2)) ≤ (⌊‘(𝐴 + (1 / 2))) ∧ (⌊‘(𝐴 + (1 / 2))) ≤ (𝐴 + (1 / 2))))) |
31 | 24, 26, 30 | mpbir2and 957 | 1 ⊢ (𝐴 ∈ ℝ → (abs‘((⌊‘(𝐴 + (1 / 2))) − 𝐴)) ≤ (1 / 2)) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 196 ∧ wa 384 ∈ wcel 1990 class class class wbr 4653 ‘cfv 5888 (class class class)co 6650 ℂcc 9934 ℝcr 9935 1c1 9937 + caddc 9939 · cmul 9941 ≤ cle 10075 − cmin 10266 / cdiv 10684 2c2 11070 ⌊cfl 12591 abscabs 13974 |
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-sep 4781 ax-nul 4789 ax-pow 4843 ax-pr 4906 ax-un 6949 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-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-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-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-riota 6611 df-ov 6653 df-oprab 6654 df-mpt2 6655 df-om 7066 df-2nd 7169 df-wrecs 7407 df-recs 7468 df-rdg 7506 df-er 7742 df-en 7956 df-dom 7957 df-sdom 7958 df-sup 8348 df-inf 8349 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-fl 12593 df-seq 12802 df-exp 12861 df-cj 13839 df-re 13840 df-im 13841 df-sqrt 13975 df-abs 13976 |
This theorem is referenced by: absrdbnd 14081 rddif2 32467 dnibndlem11 32478 knoppcnlem4 32486 cntotbnd 33595 |
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