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△ABC的内角A,B,C的对边分别为a,b,c,若△ABC的面积为a2t,则t=( )
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高一下学期数学《》真题及答案
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已知△ABC的内角A.B.C.的对边分别为abc且acosC.+csinA.-b=0.Ⅰ求角A.的大
已知△ABC的内角A.BC的对边分别为abc若cosA-C+cosB=1a=2c则角C.=.
已知△ABC的三个内角A.BC的对边分别为abc若abc成等差数列且2cos2B-8cosB+5=0
△ABC的内角A.B.C.的对边长分别为abc若则b=
设锐角三角形ABC的内角A.B.C.的对边分别为abc若a=2bsinA.则角B.=.
△ABC的内角A.B.C.的对边分别为abc若sinAsinBsinC成等比数列且c=2a则cosB
在△ABC中已知abc分别为△ABC内角ABC的对边.若b=a且sinB.+cosB.=0则A=.
△ABC的内角A.B.C.的对边分别为abc若abc成等差数列且2a=3c则cosB=
设△ABC的内角A.B.C.所对边的长分别为abc若b+c=2a3sinA=5sinB则角C.=__
在△ABC中有如下结论若点M.为△ABC的重心则设abc分别为△ABC的内角A.B.C.的对边点M.
在锐角△ABC中内角A.B.C.的对边分别为abc且2asinB.=b.1求角A.的大小2若a=6b
△ABC的内角A.B.C.的对边分别为abc已知2cosC.·acosB.+bcosA.=c.1求C
△ABC的内角A.B.C.的对边分别为abc已知2cosC.acosB.+bcosA.=c.1求C.
设△ABC的内角A.B.C.的对边分别为abc若b=2B.=C.=则△ABC的面积为.
△ABC的内角A.B.C.的对边分别为abc已知a=bcosC+csinB.1求B2若b=2求△AB
△ABC的内角
,
,
的对边分别为a,b,c,若c=2,b=6,B.=120°,则a=( ) A. 6B. 4 C. 3
2
在△ABC中内角A.B.C.的对边分别为abc已知a-b=2c=4sinA=2sinB.则△ABC的
在△ABC中内角A.B.C.的对边长分别为abc且2b-ccosA.=acosC.1求角A.的大小2
△ABC的内角A.BC的对边分别为abc若2bcosB=acosC+ccosA则B.=
△ABC在内角A.B.C.的对边分别为abc已知a=bcosC+csinBⅠ求B.Ⅱ若b=2求△AB
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如图所示甲为小型旋转电枢式交流发电机电阻为r=2Ω的矩形线圈在磁感应强度为B的匀强磁场中绕垂直于磁场方向的固定轴OO′匀速转动线圈的两端经集流环和电刷与右侧电路连接右侧电路中滑动变阻器R的最大阻值为R0=4Ω滑动片P位于滑动变阻器中点定值电阻R1=7ΩR2=2Ω其他电阻不计.从线圈平面与磁场方向平行时开始计时闭合开关S.线圈转动过程中理想交流电压表示数是10V图乙是矩形线圈磁通量随时间t变化的图象.则下列说法正确的是
假定英语课上老师要求同桌之间交换修改作文请你修改你同桌写的以下作文.文中共有10处语言错误每句中最多有两处.每处错误仅涉及一个单词的增加删除或修改.增加:在缺词处加一个漏字符号∧并在其下面写出该加的词.删除:把多余的词用斜线\划掉.修改:在错的词下划一横线并在该词下面写出修改后的词.注意:1.每处错误及其修改均仅限一词;2.只允许修改10处多者从第11处起不计分.Itisessentialtotakeanusefulsummervacationaftertheexam.Therearemanykindsofactivityforustotakepart.Firstwecanvisitourrelativesandfriendsorspendahappilytimewithourfamily.Secondseeingafilmlisteningtomusicorhangoutwithourfriendswillalsobeexcited.Thirdweshouldtakemoreexercisetokeephealthy.What'smorewe'dbettertoreviewwhatwehadlearnedatschool.Finallyitisnecessaryofustodosomehouseworkthatcanhelpourparentsalot.AboveallIhopeallofuscanhaveapleasantvacation.
设数列{an}的前n项和为Sn且2Sn=3an﹣3. 1求{an}的通项公式 2若bn=求数列{bn}的前n项和.
如图所示质量为m的小球被水平绳AO和与竖直方向成θ角的轻弹簧系着处于静止状态现将绳AO烧断在绳AO烧断的瞬间重力加速度为g.下列说法正确的是
Forsomepeoplegoingtoamuseumisanenjoyableexperience.1Howtomakemuseumsandtheirlifelesshistoricalcollectionsmoreappealing?Thisisatoughquestionthatisworthstudying. NationalTreasureaculturalexplorationprogrammewhichbegantoaironChannel3ofCCTVonDec.32017maybeagoodanswer.2. Theshowusescreativewaystoarouseinterestinthecollectionsmuseumshold.ItpresentstreasuresthroughdifferentartisticmethodsandfullyexplainsthestoriesandhistorybehindeachculturalrelicsothataudiencescannotonlyunderstandhowtoappreciatethebeautyofculturalrelicsbutalsoknowthecivilizationtheycarryandthespiritofChineseculturepreservedovertheyears.3. Theshowusesdifferentmethodsincludingdramaticperformancesanddocumentary﹣stylestorytellingtoshowthebackgroundstoriesofseveralnationaltreasures.4Whileexplainingthemysteriesbehindthetreasures.thenationaltreasurekeeperseitherfamouspeopleorordinarypeoplealsotelltheirownstories. 5ThepopularityofMastersinForbiddenCity我在故宫修文物a2016documentaryfeaturingtheForbiddenCity'sculturalrelicsencouraged15000collegestudentstoapplytoworkatthePalaceMuseumlastyear.TheshowNationalTreasurewilltouchmillionsofpeople'sheartsandencouragemorepeopletovisitmuseums. A.Forothers.it'sjustseveralhoursworthofyawning. B.Eachtreasureispresentedbyanationaltreasurekeeper. C.Itisanexcellentexampleofmakingancientrelicsalive. D.HongKongactorTonyLeungforexampleisoneofthekeepers. E.Watchingtheshow.youjustcanthelpbeingproudofChineseculture. F.Museumsaretreasurehousesthatgiveunderstandingintodifferentcultures. G.Actuallyshowspromotingtraditionalrelicshavebecomemorepopularrecently.
假定你是李华你的澳大利亚朋友Mike写信告诉你他将参加他所在城市举行的我所了解的中国传统节日'的演讲比赛希望你能为他推荐一个中国传统节日请你给他回信要点包括:1.收信时的感想2.推荐并介绍中国节日;3.预祝对方取得好成绩注意:1.词数100左右可以适当增加细节以使行文连贯2.文章开关和结尾已给出不计入总词数DearMikeYoursLiHua
已知椭圆的离心率为短轴长为过右焦点F且与x轴不垂直的直线l交椭圆于PQ两点. Ⅰ求椭圆C的方程 Ⅱ当直线l的斜率为时求△POQ的面积 Ⅲ在x轴上是否存在点Mm0满足|PM|=|QM|若存在求出m的取值范围若不存在请说明理由.
如图所示是两个分子间的引力和斥力的合力F与两分子间的距离r的关系曲线曲线与横轴的交点的横坐标为r0.若取两分子相距无穷远时分子势能为零现有两个静止的相距较远的分子假设只在分子力作用下相互接近在此过程中下列说法正确的是
ThecityofSanFranciscoisawonderfultouristattractionthatoffersmanydifferentthingstoseeanddo.Thebestwayforatravelertogetagoodlookatthecityistotakeoneofthemanydifferenttoursthere TourtheCityonFoot Whentouringthecitybywalkingyouaren'tgoingtowalkmuch.What'smoretherearefarmorebenefits.Thiskindoftourallowsyoutoseeasmanybuildingsofthecityaspossible.Atourofthecityonfootusuallyfocusesonamorelocalizedneighborhoodlevelwhichcanbeveryinterestinginanumberofdifferentways HittheWatersofSanFranciscoBay ThewatersofSanFranciscoBayhaveplayedanimportantroleinthecity'sdevelopmentoverthelastcentury.TouringSanFranciscofromthewaterisacompletelyuniquewayforyoutoseethiswonderfulcity. TakeaBusTour Ifyouwanttoseeawidevarietyofattractionsfromalloverthecity.oneofthebestthingsyoucoulddoistobookatourthroughourcompanythatoffersserviceshere.AbustourofSanFranciscoisoneofthemostcompletewaystoexperiencethecity. TourSanfranciscoFromtheAir WhileitisoneofthemostexpensivewaystoseeSanFrancisco.touringthecityfromtheairisoneofthemostuniqueandthrillingwaystoseethecity.SeeingthecityfromhighaboveallowsyoutogetafullviewofthecityastourguidespointoutattractionsfromhighaboveIfyoudodecidetotourSanFranciscobyairyou'llbecreatingmemoriesthatyouwontforgetforever. Weareatravelagencyprovidinghigh﹣qualityservicesanddiscounts.Formoreinformation.pleaseclickhere 1HowshouldyoutourSanFranciscotobestappreciateitsbuildings? A.Byair B.Bybus C.Onfoot D.Byboat 2WhatcanwelearnabouttheWatersofSanFranciscoBay? A.Theyhavehigh﹣qualityseawater. B.Theyareexploredonalocalizedlevel C.Theywerenotinuseuntilthelastcentury D.Theyhavehelpedthecitytodevelopfurther 3Whatistheauthor'spurposeinwritingthetext? A.TointroduceSanFrancisco B.Toadvertiseforatravelagency C.ToshowwhattodoinSanFrancisco D.TopersuadepeopletovisitSanFrancisco
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如图所示在粗糙的水平桌面上有均可看做质点的物体A和BAB与桌面间动摩擦因数均为μ=0.1物体B静止在桌面的右边缘.mA=mB=1kg现有一水平恒力F=3N作用在A上使A由静止向右运动在与B发生弹性碰撞前的瞬间撤去F已知AB间的L=1m桌面的高度h=0.2m重力加速度g=10m/s2求 1物体A与B碰撞前速度v1的大小 2物体B被撞飞出后的水平位移x.
等比数列{an}的前n项和为Sn若S10=10S30=30则S20=
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Eveniftreescannotwalktheyarestillonthemove. InpartsoftheArcticentireforestsaremovingnorthward.AcrosstheArctictemperaturesarerisingfasterthananywhereelseintheworld.Asthathappensthetreelinethatmarkswhereforestsstopandthetreelesstundra冻原startshasbeenshiftingnorthward.Treesgrowingalongthetreelinemustprotectthemselvesfromthecoldwind.Todothisplantstendtogrowhorizontal水平的brancheslowtotheground.Theenergyittakesfortreestogrowthiswaymeanstheydonthaveenoughenergytomakeseeds ButasEarthsclimatehasbeenwarming.treesnolongerhavetojustgrowhorizontally.Manycaninsteadgrowuptowardthesky.Thistakeslessenergy.Andwithallthatleftoverenergythesetreeshavestartedproducingmoreseeds.Thishappensespeciallyinplaceswherewhitespruce白云杉grows. WhitesprucewhichisaNorthAmericantreeisquiteabletoproducealotofseedswhichcanmovelongdistancesinthewind.Whenwind﹣blownseedsenduponthetundrabeyondthetreelinetheyeventuallycansprout发芽newtrees.Thisexplainshowaforestcanmove.Ofcoursetheprocesswouldworkonlyifthetundrawerewarmenough.Butinrecentyearsthewholeplanethasbeenwarming. Newtreeswillprovidesheltersforsomesnowkeepingthesunsraysfrommakingthewhitesurfacedisappear.Insteadthetreesabsorbthesunsheat.Thiswarmsthesurroundingair.Theextrawarmthencouragesevenmoretreestoproduceseeds.Thatfurtherboostsaforestsabilitytoexpand.Inadditionmoretreeswilltrapmoresnowpreventingmuchofitfrombeingblownaway.Snowcantrapheatinthesoilbelowwhichencouragestreestogrow.Therecentriseoftemperatureshashelpedmoretreesgrowpastthetreeline.Peopleworryaboutimpactsontheanimalsthatdependonfrozenconditionsforfoodandshelter. 1WhatisthemaincauseofthetreesintheArcticmovingnorthward? A.Thehighertemperature B.Theabundantresources C.Thefierceandcoldwind D.Theshrinkingofnortherntundra 2WhatdoestheunderlinedwordthisinParagraph2mean? A.Toproducemoreseed B.Toresistthecoldwind C.Tomovenorthward D.Torespondtotheclimatechange 3Whatcanbeinferredfromthelastparagraph? A.Newtreescantrapthesnowwhichmaymakethesoilcolder B.Thetrappedsnowpreventsnewtreesfromproducingmoreseeds C.Newtreescanmakethesurroundingairwarmer. D.Newtreescanbringmorefoodandsheltertolocalanimals. 4Thepassageismostprobablytakenfrom. A.asciencereport B.anagriculturereport C.asciencefictionmagazine D.anastronomymagazine
BackinJanuaryIwaswatchingacollegefootballgameandcametoarealization:AsahighschoolseniorprettysoonI'llbethesameageassomeofthetopathletesintheworld. Thisrealizationwasbothconfusingandcomforting.UntilthispointI'dalwaysthoughtoftopathletesinanothergeneration.IhadnorealconnectiontopeopleinthenewsorplayingsportsonTVbecausetheyweresomucholder.Butprettysoonpeopleofmyagewillbetheonesdominating支配thenews. ThecomfortcameinunderstandingthatasIpreparetograduatefromSanfordH.CalhounHighSchoolinMerrickI'mnotthatfarofffromenteringtherealworldandIwillhaveachancetomakeanameformyself. RightnowI'mattheendofoneoflifestageswithmanymoretocome.Asseniorsmanyinmyclassdevelopedsuperioritycomplexes.We'dseebabyfacedninthgradersandthinkUghthoseannoyingfreshmen.Orwe'dhearjuniorscomplainaboutstartingthecollegeapplicationprocessandsaytoeachotherThosejuniorshavenoideawhatthey'retalkingabout.Ofcourselastyear'sseniorssaidthesamethingaboutlastyear'sjuniorsrepeatingatimelesscycle. PsychologistandauthorThomasArmstrongwritesthatlifeismadeupof12stages.Hestressesthatnostageismoreimportantthananotherandeachhasitsownuniquegifts.Thereisnohighestpointinlifenoimpressiveendingwhenyouareaboveeverybodyelse.Atthesametimethereisnolowestpointinlife;atnopointisahumanworthlessandbelowothers.Justasaninfantisn'tbeloweveryoneelseoureldersaren'taboveeveryoneelse. 1Whatcanweknowabouttheauthor? A.He'llfinishhishighschoolstudiesaboutoneyearlater. B.Reflectingonthepastisapartofhisdailyroutine. C.Footballisaparticularfavoritewithhim. D.Hedreamsofbeinganexcellentathlete. 2Whydidtheauthorfindhisrealizationcomforting? A.Thetopathletesarethesameageashim. B.Thereisapossibilitythathecanbefamous. C.Hewillbeadmittedtohisdreamuniversity. D.He'smadefullpreparationsforenteringsociety. 3WhatdoestheunderlinedphrasesuperioritycomplexesinParagraph4mean? A.Ahabitofmakingcomplaints. B.Ahabitoffollowinginothers'footsteps. C.Afeelingthatyouarebetterthanothers. D.Afeelingthatothersareunapproachable. 4Whatmessageisconveyedinthelastparagraph? A.Lifeismeanttobelivedandenjoyed. B.Lifeisneversmoothfullofupsanddowns. C.Oneshouldtrytoreachhisgreatestpotential. D.Everyonehastheirownvalueandpositioninlife.
在直角坐标系xOy中直线l的参数方程为t为参数在以坐标原点O为极点以x轴正半轴为极轴建立极坐标系圆C的方程为. 1写出直线l的普通方程和圆C的直角坐标方程 2若圆C与直线l交于AB两点求的值.
Areyoucontentwiththeshapeofyournose?Ifnottheclimatemaybetoblamenotyourparents. AccordingtoarecentstudycarriedoutbyscientistsfromPennsylvaniaStateUniversityUSclimateplayedakeyroleinshapingournoses.Thefindingswerebasedonanexaminationofthesizeandshapeofnosesof476peoplefromfourregions﹣WestAfricaEastAsiaSouthAsiaandNorthernEuropeusing3﹣Dfacialimagingtechnology. PeoplehavethoughtforalongtimethedifferenceinnoseshapeamonghumansacrosstheworldmayhavearisenasaresultofnaturalselectionbecauseofclimateArslanZaidioneoftheleadauthorsofthestudytoldTheGuardian.ButwhilepreviousstudieswerebasedonmeasurementsfromhumanskullsZaidiandhisteamlookedatnoseshapeitself. Theresultshowedthatwidernosesaremorecommoninwarmandhumidclimatewhilenarrowernosesaremorecommonincoldanddryclimate.ThatZaidisaidcouldbebecausenarrowernasalpassageshelptoincreasethemoisture潮湿contentofairandwarmitwhichiseasieronourlungs.Thisinturnledtoagradualdecreaseinnosewidthinpopulationslivingfarawayfromtheequator. MorestudiesarestillneededtotestthelinkbetweenclimateandnoseshapebutZaidibelievesthecurrentfindingsarevaluableinunderstandingpotentialhealthissues.AswebecomemoreofaglobalcommunitywearegoingtocomeacrossclimatethatwedonotadapttohetoldTheGuardian.Thismeansmovingtoaverydifferentclimatemightincreasetheriskofbreathingproblems. HoweverheaddedThismaynotbenecessarilytrueforvariousreasonssuchasofmodernmedicineandthefactthatourcurrentclimateisverydifferentfromwhatitusedtobe. 1FromthepassageweknowmostpeoplefromSingaporehavenoses. A.wider B.narrower C.smaller D.larger 2Narrowernosesarehelpfulto. A.cooltheair B.warmtheair C.takeinmoreoxygen D.drytheair 3Whatcanbelearnedaboutthestudy? A.Zaidi'steammeasuredhumanskullsusing3﹣Dtechnology. B.Theshapeofournosesisdeterminedbyourparents. C.Noseshapehelpspeopleadapttotheenvironment. D.It'scertainthatpeoplewillsufferfrommorebreathingproblems. 4Whichofthefollowingcanbethebesttitleforthepassage? A.Whatfactorsshapenoses? B.Howtomakeyournoseattractive? C.Noseshapecausesbreathingproblems D.Climateshapesnoses
如图1水平地面上边长为L的正方形ABCD区域埋有与地面平行的金属管线.为探测金属管线的位置走向和埋覆深度先让金属管线载有电流然后用闭合的试探小线圈P穿过小线圈的磁场可视为匀强磁场在地面探测如图2所示将暴露于地面的金属管接头接到电源的一段将接地棒接到电源的另一端.这样金属管线中就有沿管线方向的电流.使线圈P在直线BD上的不同位置保持静止时线圈平面与地面平行线圈中没有感应电流.将线圈P静置于A处当线圈平面与地面平行时线圈中有感应电流当线圈平面与射线AC成37°角且保持静止时线圈中感应电流消失.下列说法正确的是已知sin37°=0.6cos37°=0.8
某同学为了探究物体的质量不变时加速度跟合外力的关系.将力传感器固定在小车上然后把绳的一端固定在传感器挂钩上用来测量绳对小车的拉力根据所测数据在坐标系中作出了如图所示的a﹣F图象.由于疏忽实验者忘记了平衡摩察力将带滑轮的长木板固定在水平的桌面上了. 1实验中是否需要钩码的质最远小于小车和传感器的总质量填“是“或“否” 2由图象求出小车和传感器受到的摩擦阻力为N总质量为kg
Wheneveryoufeelcold.thefirstthingyoudoistoputonmoreclothes.Butitcanhappenthatyoucanfeelcolderwhenyougooutsidewiththesameamountofclotheson1youdoindoorsWhyisthis? AccordingtoTheConversationthereason2lieincoldreceptors接收器intheskin.Whenthetemperaturedrops.thesereceptorssend3signaltotellthebrainthebodytemperature.Thenbraincreates4awareoffeelingcold. 5wearmoreclothesathomeleadstoaveragebodytemperaturebeingraised.Thenthereceptorssendthebrainthesignalofa6hightemperature.Howeverwhenyougooutsideyournervoussystemlearnsthetemperature7yourskin.inparticulartheface.Asaresultthedifferenceintemperatureisnowgreaterandyoufeeltheairiscolderparticularlyonthe8exposeskin. 9accordingtoTheSun.onceyougetoveryourinitialsenseofcoldnessyourcoatwillstilldoitsjobandyou10feelitsbenefit.
Iwasalovelychildwithalovingfamily.Iwasnotan1butaleaderinschool.Butwhatmademespecialwasnotseenfromtheoutside:Iwas2aboutlife.Mybestqualitywasmypersonality. Atagetwelvemylifehadabreakdown.ItwasthenthatIdevelopedOCD强迫症.Iwasnolongerthe3girl.IfinallytoldmymotherIwassufferingfromdepression.Istartedtakingmedicine4themedicinedidhelp.Butonethingdidn't5:Istillwasoverwhelmedwithdepression.Istillwas6sadandIstartedtobelievethatmylifenolonger7. Thinkingmylifenolongerhad8.Idecidedleavingtheworldwasthesolution.IwroteanotetoallmyfriendsandfamilyexpressingIwas9forleavingthem.AsIwasfoldingthenotemyeyesfellonaphotograph.Itwasalittlegirlwearingacarefreesmile. Ittookmeafewminutesto10whothegirlinthephotowas.I11couldn'tbelievethatsmilingchildwasme!Itseemedmyyoungerselfhadsentmea12.RightthenandthereIknewIcouldn't13myself.OnceIhadbeenastronggirlandIhadtobelikethatagain.IsworeIwouldn'tonly14mymedicine.Iwouldfightthedepressionwithmy15too. It'sbeentwoyears16Irecovered.TherealreasonI'm17isthatIrefusedtoletdepression18mylife.Ilearnedalifelong19:Nevergiveup.Lifeisgood.Everyonehas20inlifebuteveryonecansurvive.Iamlivingproofofthat. 1A.follower B.winner C.listener D.organizer 2A.curious B.upset C.concerned D.enthusiastic 3A.beautiful B.brave C.happy D.casual 4A.Afterall B.Infact C.Inaddition D.Bychance 5A.matter B.occur C.change D.arrive 6A.occasionally B.constantly C.naturally D.rarely 7A.counted B.existed C.turned D.appeared 8A.destination B.advantage C.impact D.meaning 9A.grateful B.sorry C.responsible D.suitable 10A.explain B.assume C.realize D.acknowledge 11A.never B.only C.still D.even 12A.chance B.letter C.greeting D.message 13A.forgive B.kill C.control D.betray 14A.relyon B.takeover C.bringin D.pickout 15A.mind B.choice C.decision D.imagination 16A.after B.since C.before D.when 17A.educated B.praised C.healed D.accepted 18A.break B.define C.fail D.ruin 19A.memory B.story C.lesson D.concept 20A.challenges B.promises C.opportunities D.options
在锐角△ABC中角ABC所对的边分别是abc且acosC=csinA. 1求C 2若△ABC的面积为8a=4求b的值.
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