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Mirrors > Home > MPE Home > Th. List > Mathboxes > reabssgn | Structured version Visualization version GIF version |
Description: Alternate expression for the absolute value of a real number. (Contributed by RP, 22-May-2024.) |
Ref | Expression |
---|---|
reabssgn | ⊢ (𝐴 ∈ ℝ → (abs‘𝐴) = ((sgn‘𝐴) · 𝐴)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | rexr 10710 | . . . 4 ⊢ (𝐴 ∈ ℝ → 𝐴 ∈ ℝ*) | |
2 | sgnval 14480 | . . . 4 ⊢ (𝐴 ∈ ℝ* → (sgn‘𝐴) = if(𝐴 = 0, 0, if(𝐴 < 0, -1, 1))) | |
3 | 1, 2 | syl 17 | . . 3 ⊢ (𝐴 ∈ ℝ → (sgn‘𝐴) = if(𝐴 = 0, 0, if(𝐴 < 0, -1, 1))) |
4 | 3 | oveq1d 7158 | . 2 ⊢ (𝐴 ∈ ℝ → ((sgn‘𝐴) · 𝐴) = (if(𝐴 = 0, 0, if(𝐴 < 0, -1, 1)) · 𝐴)) |
5 | ovif 7238 | . . . 4 ⊢ (if(𝐴 = 0, 0, if(𝐴 < 0, -1, 1)) · 𝐴) = if(𝐴 = 0, (0 · 𝐴), (if(𝐴 < 0, -1, 1) · 𝐴)) | |
6 | ovif 7238 | . . . . 5 ⊢ (if(𝐴 < 0, -1, 1) · 𝐴) = if(𝐴 < 0, (-1 · 𝐴), (1 · 𝐴)) | |
7 | ifeq2 4418 | . . . . 5 ⊢ ((if(𝐴 < 0, -1, 1) · 𝐴) = if(𝐴 < 0, (-1 · 𝐴), (1 · 𝐴)) → if(𝐴 = 0, (0 · 𝐴), (if(𝐴 < 0, -1, 1) · 𝐴)) = if(𝐴 = 0, (0 · 𝐴), if(𝐴 < 0, (-1 · 𝐴), (1 · 𝐴)))) | |
8 | 6, 7 | ax-mp 5 | . . . 4 ⊢ if(𝐴 = 0, (0 · 𝐴), (if(𝐴 < 0, -1, 1) · 𝐴)) = if(𝐴 = 0, (0 · 𝐴), if(𝐴 < 0, (-1 · 𝐴), (1 · 𝐴))) |
9 | 5, 8 | eqtri 2782 | . . 3 ⊢ (if(𝐴 = 0, 0, if(𝐴 < 0, -1, 1)) · 𝐴) = if(𝐴 = 0, (0 · 𝐴), if(𝐴 < 0, (-1 · 𝐴), (1 · 𝐴))) |
10 | mul02lem2 10840 | . . . . . 6 ⊢ (𝐴 ∈ ℝ → (0 · 𝐴) = 0) | |
11 | 10 | adantr 485 | . . . . 5 ⊢ ((𝐴 ∈ ℝ ∧ 𝐴 = 0) → (0 · 𝐴) = 0) |
12 | simpr 489 | . . . . . 6 ⊢ ((𝐴 ∈ ℝ ∧ 𝐴 = 0) → 𝐴 = 0) | |
13 | 12 | abs00bd 14684 | . . . . 5 ⊢ ((𝐴 ∈ ℝ ∧ 𝐴 = 0) → (abs‘𝐴) = 0) |
14 | 11, 13 | eqtr4d 2797 | . . . 4 ⊢ ((𝐴 ∈ ℝ ∧ 𝐴 = 0) → (0 · 𝐴) = (abs‘𝐴)) |
15 | recn 10650 | . . . . . . . 8 ⊢ (𝐴 ∈ ℝ → 𝐴 ∈ ℂ) | |
16 | 15 | mulm1d 11115 | . . . . . . 7 ⊢ (𝐴 ∈ ℝ → (-1 · 𝐴) = -𝐴) |
17 | 15 | mulid2d 10682 | . . . . . . 7 ⊢ (𝐴 ∈ ℝ → (1 · 𝐴) = 𝐴) |
18 | 16, 17 | ifeq12d 4434 | . . . . . 6 ⊢ (𝐴 ∈ ℝ → if(𝐴 < 0, (-1 · 𝐴), (1 · 𝐴)) = if(𝐴 < 0, -𝐴, 𝐴)) |
19 | reabsifneg 40690 | . . . . . 6 ⊢ (𝐴 ∈ ℝ → (abs‘𝐴) = if(𝐴 < 0, -𝐴, 𝐴)) | |
20 | 18, 19 | eqtr4d 2797 | . . . . 5 ⊢ (𝐴 ∈ ℝ → if(𝐴 < 0, (-1 · 𝐴), (1 · 𝐴)) = (abs‘𝐴)) |
21 | 20 | adantr 485 | . . . 4 ⊢ ((𝐴 ∈ ℝ ∧ ¬ 𝐴 = 0) → if(𝐴 < 0, (-1 · 𝐴), (1 · 𝐴)) = (abs‘𝐴)) |
22 | 14, 21 | ifeqda 4449 | . . 3 ⊢ (𝐴 ∈ ℝ → if(𝐴 = 0, (0 · 𝐴), if(𝐴 < 0, (-1 · 𝐴), (1 · 𝐴))) = (abs‘𝐴)) |
23 | 9, 22 | syl5eq 2806 | . 2 ⊢ (𝐴 ∈ ℝ → (if(𝐴 = 0, 0, if(𝐴 < 0, -1, 1)) · 𝐴) = (abs‘𝐴)) |
24 | 4, 23 | eqtr2d 2795 | 1 ⊢ (𝐴 ∈ ℝ → (abs‘𝐴) = ((sgn‘𝐴) · 𝐴)) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 → wi 4 ∧ wa 400 = wceq 1539 ∈ wcel 2112 ifcif 4413 class class class wbr 5025 ‘cfv 6328 (class class class)co 7143 ℝcr 10559 0cc0 10560 1c1 10561 · cmul 10565 ℝ*cxr 10697 < clt 10698 -cneg 10894 sgncsgn 14478 abscabs 14626 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1798 ax-4 1812 ax-5 1912 ax-6 1971 ax-7 2016 ax-8 2114 ax-9 2122 ax-10 2143 ax-11 2159 ax-12 2176 ax-ext 2730 ax-sep 5162 ax-nul 5169 ax-pow 5227 ax-pr 5291 ax-un 7452 ax-cnex 10616 ax-resscn 10617 ax-1cn 10618 ax-icn 10619 ax-addcl 10620 ax-addrcl 10621 ax-mulcl 10622 ax-mulrcl 10623 ax-mulcom 10624 ax-addass 10625 ax-mulass 10626 ax-distr 10627 ax-i2m1 10628 ax-1ne0 10629 ax-1rid 10630 ax-rnegex 10631 ax-rrecex 10632 ax-cnre 10633 ax-pre-lttri 10634 ax-pre-lttrn 10635 ax-pre-ltadd 10636 ax-pre-mulgt0 10637 ax-pre-sup 10638 |
This theorem depends on definitions: df-bi 210 df-an 401 df-or 846 df-3or 1086 df-3an 1087 df-tru 1542 df-fal 1552 df-ex 1783 df-nf 1787 df-sb 2071 df-mo 2558 df-eu 2589 df-clab 2737 df-cleq 2751 df-clel 2831 df-nfc 2899 df-ne 2950 df-nel 3054 df-ral 3073 df-rex 3074 df-reu 3075 df-rmo 3076 df-rab 3077 df-v 3409 df-sbc 3694 df-csb 3802 df-dif 3857 df-un 3859 df-in 3861 df-ss 3871 df-pss 3873 df-nul 4222 df-if 4414 df-pw 4489 df-sn 4516 df-pr 4518 df-tp 4520 df-op 4522 df-uni 4792 df-iun 4878 df-br 5026 df-opab 5088 df-mpt 5106 df-tr 5132 df-id 5423 df-eprel 5428 df-po 5436 df-so 5437 df-fr 5476 df-we 5478 df-xp 5523 df-rel 5524 df-cnv 5525 df-co 5526 df-dm 5527 df-rn 5528 df-res 5529 df-ima 5530 df-pred 6119 df-ord 6165 df-on 6166 df-lim 6167 df-suc 6168 df-iota 6287 df-fun 6330 df-fn 6331 df-f 6332 df-f1 6333 df-fo 6334 df-f1o 6335 df-fv 6336 df-riota 7101 df-ov 7146 df-oprab 7147 df-mpo 7148 df-om 7573 df-2nd 7687 df-wrecs 7950 df-recs 8011 df-rdg 8049 df-er 8292 df-en 8521 df-dom 8522 df-sdom 8523 df-sup 8924 df-pnf 10700 df-mnf 10701 df-xr 10702 df-ltxr 10703 df-le 10704 df-sub 10895 df-neg 10896 df-div 11321 df-nn 11660 df-2 11722 df-3 11723 df-n0 11920 df-z 12006 df-uz 12268 df-rp 12416 df-seq 13404 df-exp 13465 df-sgn 14479 df-cj 14491 df-re 14492 df-im 14493 df-sqrt 14627 df-abs 14628 |
This theorem is referenced by: (None) |
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