how to get precise conversion in matlab?

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Mudasir Ahmed
Mudasir Ahmed 2015-12-22
评论： Mudasir Ahmed 2015-12-24
hi
when i want to convert degrees(89.999999999999668207879992402105) into radians matlab gives 1.5707963267948966192313216916398 value as a output. but when i reverse the process it gives round off figure 90. but i need actual and accurate conversion value not the round off.*
vpa(89.999999999999668207879992402105*pi/180)
ans = 1.5707963267948966192313216916398
but when re-convert back to original form
vpa(1.5707963267948966192313216916398*180/pi)
ans = 90.0
i also change the the number of digits like vpa(1.5707963267948966192313216916398*180/pi,100) etc but observe the same results. kindly help me i will be highly thankful to you for this act of kindness
with best regards mudasir ahmed

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采纳的回答

Walter Roberson
Walter Roberson 2015-12-22
Every time you use a literal number in MATLAB that is not inside a string, MATLAB is going to evaluate the number as double precision before the Symbolic toolbox gets control. You need to quote your numbers. You should also get in the habit of sym()'ing them
vpa('89.999999999999668207879992402105*pi/180')
vpa('1.5707963267948966192313216916398*180/pi')
but better
vpa(sym('89.999999999999668207879992402105*pi/180'))
vpa(sym('1.5707963267948966192313216916398*180/pi'))
  6 个评论
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Walter Roberson
Walter Roberson 2015-12-23
编辑：Walter Roberson 2015-12-23
Where are those numbers coming from? What is class(angles) ?
As far as double precision numbers are concerned, 89.999999999999667479426986067257 and 89.999999999999668207879992402105 are the same number, both of them being 89.9999999999996731503415503539144992828369140625 . That is something that cannot be changed with double precision numbers. You need to use some kind of extended precision numbers if you want them to be different, and using extended precision numbers will require a different syntax to enter the numbers.
angles= [
sym('88.25292994445806042220189637777'), sym('89.999999999999667479426986067257'), sym('89.999999999999668207879992402105');
sym('86.472119235585302296157262009321'), sym('89.999999999981123270039862159233'), sym('89.999999999999993121983558088696');
sym('84.665084516953164820028709815801'), sym('89.999988086384753274282238804303'), sym('89.999999999999999806246175977474');
sym('82.83552790044595696067282049508'), sym('89.999999999999991112449117158209'), sym('89.999999999999993100744665396289');
sym('80.986484951716410032164762120977'), sym('89.999999999959332692365063960468'), sym('89.999999999999993122476505390389');
sym('79.121948083059506104642254539888'), sym('89.999999975262684086292374865148'), sym('89.999999975262721970224316791639');
sym('77.244683750911755612284108834821'), sym('89.999999986727214128999425244292'), sym(' 89.999999999999993118675432116');
sym('75.357853348492194774432573472921'), sym('89.999999996394470554515857407735'), sym('89.999999999999993122326059745969');
sym('73.464609154556051725140093954363'), sym('89.999999999999992753073655039909'), sym(' 89.99999999999999312244662902997');
sym('71.567882600107703152375030768898'), sym('89.999999999999992581194507627371'), sym('89.999999999999903122444226118167');
sym('69.670377917650110578302342213061'), sym(' 89.99999999999999253319867704809'), sym('89.999999999999993122506541238628');
sym('67.774518693860294741798881967926'), sym('89.999999999741931635361989813778'), sym(' 89.99999999999999311361444679491');
sym('65.8822150925780553458648880066'), sym('89.999999999999993098178222946334'), sym('89.999999999999993098179444490446');
sym('63.995531641271152333402009895049'), sym(' 89.99999999999998928710524083006'), sym('89.999999999999989287200958233939');
sym('62.11650712167783271029169712539'), sym('89.999999999999992778649497157995'), sym('89.999999999999993114151872373191');
sym('60.248879494097092226691703377443'), sym('89.999999714196263418663102999409'), sym('89.999999714228313385429057755702');
sym('58.403778779168425376458768895025'), sym('89.999999999137259749938314739589'), sym('89.999999999137259749982719609229');
sym('56.981178198306788453173114217814'), sym('89.762868470688394985205767662633'), sym('89.762868476395663591421156348161');
sym('55.797765504938677490457342932495'), sym('89.373318780644193165202171792606'), sym('89.373318781818103518674315233533');
sym('54.587935182089116272733342933166'), sym('88.990431406326516856547028587032'), sym('88.990431406591153148197145112555');
sym('53.354014335890068423930796964625'), sym('88.614043918721599881539781770388'), sym('88.614043920256183958551643928488');
sym('52.102828587990070160284343107814'), sym(' 88.2428950103448063709444005364'), sym('88.242895010344837842115341055113');
sym('50.847370222094078935464371138828'), sym('87.874480590803891405154343446749'), sym('87.874480590804517899382996732148');
sym('49.608305531180989583106115411603'), sym('87.505432535307217476773269948055'), sym('87.505432535865023730893742717288');
sym('48.415797409309773763494041129682'), sym('87.133249369666402388158308284657'), sym(' 87.13324953896692912915248042765');
sym('47.319006419412375441482463740122'), sym('86.762822149627226035956852057888'), sym('86.762822149627228080575948403545');
sym('46.582079859159937061510793780591'), sym('85.719451610184566072659221879479'), sym('87.244618123174325584003266671315');
sym('46.066041618599459232573510370179'), sym('82.026624770981104993564747832309'), sym('89.000000000000003122506798154241');
sym('45.386778108921029448330688915442'), sym('81.056639804856155393782241508934'), sym(' 89.00000000000000312247901974552');
sym('44.810709922770479654022899731807'), sym(' 79.85140653285072910261889475959'), sym('89.000000000000003121517090477509');
sym('44.407994718303529322012130356452'), sym('78.406341220762609832287704998145'), sym('89.000000000000003122506695222577');
sym('44.177863358331681247268470314704'), sym('76.663658074969014950975482110977'), sym('89.000000000000003122362329641815');
sym('43.959810840916627632291752292788'), sym('73.526831898059132595944316095278'), sym('89.000000000000003122504187530516');
sym('43.694419499184883392828891264002'), sym(' 71.75826883167902918068982670604'), sym('89.000000000000003121788745062828');
sym('43.251027741546380039207997137945'), sym('70.234204727031649621801943389907'), sym('89.000000000000003122474996583343');
sym('42.637418116998151402898983978727'), sym('68.912769676021656973403748785698'), sym('89.000000000000003032880353561533');
sym('41.898435136021901434977609783495'), sym('67.773923707251102112336590588202'), sym('89.000000000000003122504697427467');
sym('41.184836475454770526169624685702'), sym('66.903523494547958673973603864466'), sym('89.999999999999833536432947613648');
sym('40.862428381239072388102799260482'), sym('66.084460073179689509157465280485'), sym('89.522829700704316787172015822126');
sym('40.540636516266952240290820560618'), sym('65.126856819772530912519556002545'), sym('88.885960217714551629279716649383');
sym('40.255659784465259598431523791579'), sym('64.179840758641944635799072580719'), sym('88.207464330630301643708029281103');
sym('40.010850945561494237717302179161'), sym('63.241575921375690128896697217686'), sym('87.487400817245291516764549854452');
sym('39.808713467498020600905167414088'), sym('62.310121158268191017439073675237'), sym('86.724205099590538795832209618294');
sym('39.651235699137941154002866223805'), sym('61.387356173012999132998791694196'), sym(' 85.91804512572354531908684362598');
sym('39.538165194430280277915644799375'), sym('60.474250224993075081920867482213'), sym('85.067062469592128985115362682617');
sym('39.466960110666933148365305580884'), sym('59.573532356428610582620723516641'), sym('84.169326156839994722851898365978');
sym('39.432015845884450041682328081975'), sym('58.691141415603703186188852732795'), sym('83.224154081908098098508638307682');
sym('39.423721721040762557018620661906'), sym('57.835912725846163986993181391419'), sym('82.231710005217201980940318929372');
sym('39.427854203804045936737648421399'), sym('57.017100025090666114824479945582'), sym('81.189279997945968027347943050819');
sym('39.42505232601452888509690209578'), sym('56.249739658269332912940637300166'), sym('80.096660166863752270670416837442');
sym('39.390647447196684122821808748718'), sym('55.554432288866649394544143908114'), sym('78.956794112988051435129100678996');
sym('39.295485434138460655069960782315'), sym('54.953114909013826829509310430046'), sym('77.770798037323940758694874186351');
sym('39.106436458825812238377876015907'), sym('54.466546953908171183194461748773'), sym('76.532876400986841674072654241597');
sym('38.793346478561563885338769852014'), sym('54.120399281175709446322937865147'), sym('75.254931673637856533630653734693');
sym('38.330331127711641851815067265581'), sym('53.927323291318870022982211863696'), sym('73.937833541301955656658610212964');
sym('17.088336490954339743320153482257'), sym('49.063555853518496847132695282611'), sym('86.047629575645551833491762427327');
sym('16.138569401829393302518657353023'), sym('47.609081651809559546929063777857'), sym('85.687450126216674276932334350917');
sym('15.006475424769433438288650255401'), sym('45.977935577213604395403971235973'), sym('85.458978723833229830146633948827');
sym('13.619921345600788002490770721217'), sym('44.078709299048245947591214648017'), sym('85.426302992581532156656023919662');
sym('11.8267650623723926497981201656'), sym('41.712142445713757074070877012241'), sym('85.715080131695754408779817641065');
sym('9.2245296243075231345408544818852'), sym('38.299037256485604674692363795935'), sym('86.666411504850157482944820068921');
sym('5.1388074134133179210918029726465'), sym('30.843701804839442708201058844684'), sym('89.000000000000003122351467095414');
sym('28.959785727621613973517205409994'), sym('54.325495430170720034364047354408'), sym('64.413455707717931471957842514634');
sym('27.300263679611003321724553761333'), sym(' 53.40589763966739257758376287618'), sym('64.201206002843651134925162070302');
sym('25.62282243403643143500417851977'), sym('52.123521237961941855752478708157'), sym('64.256742505487985426401814667469');
sym('23.974934495670188034831815641503'), sym('50.610887465555046818907822300253'), sym(' 64.42902804551721983255616881651');
sym('22.393617675833419721572977100908'), sym('48.983754817517843921699882905277'), sym(' 64.58777051075157160282839204065');
sym('20.9136705221437470819555683003'), sym('47.330951777057346264087673835005'), sym('64.649303247434845792310399744472');
sym('19.552736292111277733563303438249'), sym('45.704802598671202874024285901832'), sym(' 64.57638555534845735610850884807');
sym('18.303004911231574024589890716086'), sym('44.115175486918536557716106802083'), sym(' 64.36236010002650130446682268459');
sym('17.162176457503987920893415185285'), sym('42.570027260737358172789268488225'), sym('64.017828883422816119207996253756');
sym('16.120123743171187924138480960379'), sym('41.060901322245796730887839713783'), sym('63.558787904260808428485984774223');
sym('15.166787409098382995826927992926'), sym(' 39.57207210327954701605610969234'), sym('62.999463759677363774229270520181');
sym('14.301439336879539867450684659215'), sym('38.094384784038862633711645600066'), sym('62.354253677110472521393429410139');
sym('13.526832297231141653098236378403'), sym('36.616770587520529103625710863017'), sym('61.634524238867484228443610224466');
sym('12.850501310778781306222068328247'), sym('35.126883705709719841402168873312'), sym('60.848444575878857649176841110459');
sym('12.284397912758216491110610479016'), sym(' 33.60675249292420351290535089423'), sym('59.998875787093948993659901232047');
sym('11.850657253299977011459150618238'), sym('32.043625573573381396489406033223'), sym('59.090265841925510609666078241094');
sym('11.578458542097010605365011465385'), sym('30.422986869093006618461491586559'), sym('58.126530416235207016291855738527');
sym('11.504263485735878495047308258173'), sym(' 28.71572390735581123066212518705'), sym('57.105329541189146473954034925919');
sym('11.678732472807425838154168030856'), sym('26.886189539992739528140603212764'), sym('56.027010863763760399102906686034');
sym('12.181306720144578013295213987822'), sym('24.859896939437277868477685302965'), sym('54.886481012736021475711619783746');
sym('13.184370198537854836016299301885'), sym('22.468617738031179119546537731579'), sym('53.681045085177236860613126547676');
sym('15.642414758797712348570085462682'), sym('18.748259766124868423160203703476'), sym('52.401564526560994561415411772799');
sym('16.9508665100419632846198400422'), sym('16.950866510041963793699713245751'), sym('51.740960676360972733385568307922');
sym('16.498212382502374803847658602886'), sym('16.498212382692138566414870516934'), sym('50.402561559214755262635615502243');
sym('15.919905061949010353340137349393'), sym('15.919905061949010413452495414692'), sym('48.674082816172438711434825843997');
sym('15.183925314231711540908280773759'), sym('15.183925314261638594109821471355'), sym('46.476547248247282760657883572379');
sym('13.412731496284297607231295000985'), sym('13.412731496523672719107295235403'), sym('41.252575359960835968731759787589');
sym('12.714440699371424835588987115622'), sym('12.714440699371426022738711185432'), sym('39.141116126870159748204294086147');
sym('12.186838895206284480010663039331'), sym('12.186838895238221924881752059544'), sym('37.452396542858788255661055148553');
sym('7.600148345944255809874815387914'), sym('15.556265751981246969820316657954'), sym('36.289755985020056214898092792324');
sym('0.0000000000000031922172083790895440123007852701'), sym('17.921422936799498618476457878867'), sym('34.872114308935505260139893222266');
sym('0.000000000000013161458532581005948154928445771'), sym('17.434764669812986472753895945526'), sym('33.670396354896374198562337436628');
sym('0.00000000028643072306544462460669910260623'), sym('16.913669506785211610166569111438'), sym('32.006505847327203996890387585791');
sym('0.00000000025303621218320715713595039830793'), sym('16.561564817383445960663272025325'), sym('30.002218759573927269136189010233');
sym('0.00000000049538621296507250113310323848921'), sym('16.603361740208815054040574393569'), sym('27.558765435517896448831430971234');
sym('0.00000000022796327950043512563397227058782'), sym('17.631108143238673261963545038128'), sym('24.170514514119890139717605257263');
sym('4.018646510795218826538722177555'), sym('19.438461505599588429240452317561'), sym('19.439167200283906564736128157213');
sym('0.0000000000000000031052008141318308720142949148162'), sym('19.653908916254078761677904582833'), sym('19.653908916254078763091318017406]');

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