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在△ABC中,2sinA•sinB=tanA•tanB. (Ⅰ)求∠C的大小; (Ⅱ)求sinA-cosB的取值范围.
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在△ABC中∠A.=90°tanB.=.若以A.B.为焦点的椭圆经过点C.则该椭圆的离心率e=.
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直角三角形
有一个角是60°的三角形
如图在Rt△ABC中∠C=90°AB=20sinA=求BC的长和tanB.
已知A.B.C.是三角形的内角sinA.-cosA.是方程x2-x+2a=0的两根.1求角A.2若=
在△ABC中2sinA•sinB=tanA•tanB. Ⅰ求∠C的大小 Ⅱ求sinA﹣cosB
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AhutongisanancientcitystreettypicalinBeijing.1surroundtheForbiddenCitymanywerebuiltduringtheYuanMingandQing2dynasty.Inordertoestablishthestrongestpowerforemperorstheyplannedthecityandarrangedtheresidentialareas.3centerofthecityBeijingwastheroyalpalace﹣theForbiddenCity. AttheendoftheQingdynastyafter4closeChinacameunderinfluencefromabroadmanyoldhutongslost5theyformerneatarrangement. AfterthefoundingofthePeople'sRepublicofChinain1949hutongconditions6improve.Butinrecentyearsthehousesinmanyhutongshavebeenpulled7andreplacedbymodembuildings.Andthehutongtodayisfadingintotheshadefor8touristsandlocalpeople. HoweverintheurbandistrictofBeijinghousesalonghutongsstilloccupyone9threeofthetotalareaprovidinghousingforhalfpopulationsomanyhutongs10survive.InthisrespectweseetheoldinthenewinBeijingasanancientyetmoderncity.
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Youneverknowwhatnaturehaspreparedforyouasagift.YearsagowhenwalkingaloneonabeachinremotesouthwestFloridaIwasso1tohearsplashes水溅声comingfromthewater.AsIwalkedinthe2ofthesoundsIsawamanatee海牛showitsheadoutofthewater3agreatsnuffling带鼻音的breath.Itseemedthatitwasin4andtryingtogetoutofit. I'dneverseena5likethisbefore.Iwantedtoaskforhelpbuttherewasnoone6.SoIwentintotheshallowwaterandwenttowardtheanimal.Icame7enoughtomakeoutthemanatee.Thenasecondmanateemuchsmallerappearedbesideit.8theothermanateeswerealsomovingtowardme.SoonIwas9byseveralmanatees.Icouldclearlyseethelargermanatee10thelittleoneupwithherflipper鳍状肢andpushedittothesurfacebesideme. Asthetwoslippedunderwatertwoothermanateesmovedupfrombehindoneoneitherside11 gentlyagainstmybodyastheyswampast.Theycircledand12theactionthistime13bythemotherandherbaby.Iheldmyhandouttouchingtheirbackastheypassedme.SincetheyobviouslyenjoyedtouchingmeIbegan14eachofthemastheyswamby. Istoodthereenjoyingthescene15tomoveuntilfinallytherisingtide16mebacktotheshore.LaterIknewexactlywhattookplacethatmorning.ThemanateesinvolvedmeintheircelebrationofabirthandIwaswelcometomeetthe17memberoftheirfamily. DuringthatunexpectedsceneIfeltmoreinvolvedintherhythmsof18onourearththanever.EachyearIheadforthat19foraquietlittlebirthdaypicnicontheshore.Afterallyouneverknowwhomight20upforyourparty. 1A.frustrated B.surprised C.embarrassed D.disappointed 2A.direction B.condition C.middle D.side 3A.makingout B.puttingout C.comingout D.lettingout 4A.force B.trouble C.loss D.action 5A.look B.feel C.scene D.smell 6A.inhand B.insight C.intheway D.inthedistance 7A.close B.soon C.quick D.straight 8A.Luckily B.Personally C.Unexpectedly D.Sadly 9A.watched B.surrounded C.attacked D.separated 10A.turn B.eat C.throw D.hold 11A.rubbing B.preventing C.surfing D.comforting 12A.practiced B.changed C.repeated D.showed 13A.seen B.followed C.taught D.ordered 14A.moving B.hitting C.catching D.touching 15A.unwilling B.ready C.unable D.afraid 16A.invited B.forbade C.forced D.helped 17A.best B.oldest C.toughest D.newest 18A.life B.music C.world D.development 19A.boat B.hill C.beach D.manatee 20A.build B.show C.look D.step
2017年人类第一次直接探测到来自双中子星合并的引力波.根据科学家们复原的过程在两颗中子星合并前约100s时它们相距约400km绕二者连线上的某点每秒转动12圈将两颗中子星都看作是质量均匀分布的球体由这些数据万有引力常量并利用牛顿力学知识可以估算出这一时刻两颗中子星
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ItisoneoftheliveliestfestivalsthathappeninBathanditisreturningthisSeptember.TheJaneAustenFestivalkicksoffonSeptember8andrunsfortendaysuntilSeptember17witheventsrunningeverydayandevening. Whataresomeofthefestivalhighlights? GrandRegencyCostumedCharityWalk Thehighlightisusuallythewalkwhichsees600ormorefansdressedinperioddressastheywalkfromRoyalCrescentLawnthroughthecitytoParadeGardens.ItisasplendidsighttoseeinthehistoricGeorgianstreets. WhenSaturdaySeptember9/1100am﹣1230pm WhereRoyalCrescentLawn Tickets£10peradult/FREEtowatch MrWickhamandaneveningwithJaneAusten JaneAusten'smostmemorablecharacterscometolifeattheOldTheatreRoyal.PerformancesincludethehandsomeWickhamAdrianLukis.PeriodmusicandatalkfromhistorianCatherineCurzonwillalsofeature. WhenSundaySeptember10/730pm﹣900pm WhereTheMasonicHallOldTheatreRoyal RegencyDanceWorkshops Thereisnothinglikedancing.Afterall.Iconsideritasoneofthefirstrefinementsofpolishedsocieties…Joininonthefun.Costumesarewelcomebutnotnecessary! WhenThursdaySeptember14/Beginners1030am﹣1200pm/Improvers130pm﹣300pm WhereAssemblyRooms Tickets£15 Arethereanyfreeevents? Yes. AReadingofNorthangerAbbey.Thenovelwillbereadaloudthroughoutthefestival.SectionsofAusten'sfirstnovelaresetinBathandyoucanstillfindthelocationsmentioned! WhenEverydayfromSept.10﹣Sept.17from200pm﹣300pm WhereWaterstonesbookshopMilsomStreetupstairs 1Whatdoestheauthorsayaboutthefestival? A.Itisinhonorofanovel. B.ItstartsonSeptember8. C.ItisheldbeyondBath. D.Itisintendedforthelocals. 2Whereshouldpeoplewearspecialcostumestoattendanevent? A.RoyalCrescentLawn. B.TheMasonicHall C.AssemblyRooms. D.Waterstonesbookshop. 3Whichofthefollowingchargesnomoney? A.JoiningintheGrandRegencyCostumedCharityWalk. B.Attendingalecturefromahistorian. C.GettingAusten'snovelinabookshop. D.Enjoyingthepublicreadingofanovel.
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Foodisextremelyimportanttoushumanbeingsandriceisoneofthemainfoodintheworld.Australianresearchershavediscoveredawaytogeneticallyengineerricewhichwouldprovidesignificanthealthbenefitstomorethanhalftheworld'spopulation. AstudyundertakenattheUniversityofTasmaniapublishedinarespectedjournaloftheNationalAcademyofSciencesdiscoveredamethodtoincreasetheresistantstarch抗性淀粉contentinricemakingitmoredigestibleandleadingtolowerrateofdiabetes糖尿病andoverweight. StevenSmiththeleadauthorofthestudyandaforeignexpertfortheChinesegovernmentwhohasbeenappointedtoworkoncropimprovementprojectsbytheChineseAcademyofSciencessaidincreasingthehigherresistantstarchcontentgavethisdesignerricemanyaddedhealthbenefits.WehavediscoveredthatwecanincreasetheamountofresistantstarchincookedricewhichcouldprovidehealthbenefitsforalargenumberofpeopleinAsiaandbeyondSmithsaidinamediareleaseonFriday.Thesameapproachcanbeadaptedforuseinothercerealsincludingwheat.Notonlycanithavebenefitsfordiabetesandobesitybutalsofordisordersofthebowel肠includingcancer. Riceisthemainfoodformorethanhalftheworld'spopulationprovidingmuchoftheworldwithmostoftheircalories.SmithsaidthatastherateofdiabetesandobesityinAsiancountriescontinuedtogrowhisdesignerricecouldprovideawaytolimithealthproblems. Notonlydoesresistantstarchreducethepossibilityofa‘sugarhit'butitalsoreducestheappetiteandpromotesthegrowthofthehealthygerms.Smithsaid. SmithdivideshistimebetweentheUniversityofTasmaniaandhisresearchlabinBeijingwherehehopestomakesignificantadvanceinsustainable可持续的living. 1Whatdoweknowaboutthestudy? A.ItispartofChinesecropimprovementprojects. B.Itwillhaveasignificanteffectoncropresearches. C.Itwasjointly联合地carriedoutbyAustraliaandChina. D.Ithelpssolvethefoodproblemforoverhalfoftheworld'spopulation. 2Basedonthetexttheresistantstarch. A.existsinlargeamountsincookedrice B.decreasesthepossibilityofasugarhitandprovidesmorecalories C.ishelpfulindigestionandlowerstherateofoverweightanddiabetes D.increasespeople'sappetiteandimprovesthegrowthofhealthygerms 3TheunderlinedworditinParagraph3refersto. A.resistantstarch B.cookedrice C.theapproach D.mediarelease 4Wheredoesthistextprobablycomefrom? A.Anenvironmentalreport. B.Amedicaljournal. C.Anengineeringtextbook. D.Anagriculturalmagazine.
在某单位的职工食堂中食堂每天以3元/个的价格从面包店购进面包然后以5元/个的价格出售.如果当天卖不完剩下的面包以1元/个的价格全部卖给饲料加工厂.根据以往统计资料得到食堂每天面包需求量的频率分布直方图如下图所示.食堂某天购进了80个面包以x单位个60≤x≤110表示面包的需求量T单位元表示利润. Ⅰ求T关于x的函数解析式 Ⅱ根据直方图估计利润T不少于100元的概率.
某同学设计了如图甲所示的电路来测量电源电动势E及电阻R1和R2的阻值.实验器材有待侧电源E不计内阻待测电阻R1待测电阻R2电压表V量程为1.5V内阻很大电阻箱R0~99.99Ω单刀单掷开关Sl单刀双掷开关S2导线若干. 1先测电阻R1的阻值.请将该同学的操作补充完整 A.闭合Sl将S2切换到a调节电阻箱R读出其示数R0和对应的电压表示数U1 B.保持电阻箱示数不变读出电压表的示数U2 C.则电阻R1的表达式为R1=. 2该同学已经测得电阻Rl=4.8Ω继续测电源电动势E和电阻R2的阻值.他的做法是闭合Sl将S2切换到a多次调节电阻箱读出多组电阻箱示数R和对应的电压表示数U由测得的数据绘出了如图乙所示的﹣图线则电源电动势E=V电阻R2=Ω结果保留两位有效数字.
“跳一跳”小游戏需要操作者控制棋子离开平台时的速度使其能跳到旁边平台上.如图所示的抛物线为棋子在某次跳跃过程中的运动轨迹其最高点离平台的高度为h水平速度为v若质量为m的棋子在运动过程中可视为质点只受重力作用重力加速度为g则
Modemlifeismakinguslonelierandrecentresearchindicatesthatthismaybethenextbiggestpublichealthissuefollowingobesityandsubstanceabuse.1Changesinmodemsocietyareconsideredtobethecause.Weliveinnuclearfamilyunitsoftenlivinglargedistancesawayfromourextendedfamilyandfriendsandourgrowingrelianceonsocialtechnologyratherthanface﹣to﹣faceinteractionisthoughttobemakingusfeelmoreisolated孤立的. 2Relocatingtoanewarealosingalovedoneandstartingacourseatuniversityareallkeytimeswhenpeoplefeellonely.Somepeoplebelievethisexperienceoflonelinessmotivatesustoreconnectwithothersandtoseekoutnewfriendshipstoreducethesocialpainthatwefeel.3Butforsomewhenreconnectionisnoteasyornotpossibleandapersonissociallyisolatedhecanremaininthisuncomfortablelonelinessstateforanumberofyearswhichislinkedtopoormentalhealth. Thereareanumberofmisunderstandingsregardingthosewhoexperienceloneliness.Certainlyallofusfeelitfromtimetotime.4Theymaybesociallyisolatedduetodecreasedmobilityandlossoffriendsandpartners.Butitisnotoftenacknowledgedthatlonelinessalsoaffectspeopleatallagesincludingchildrenandisparticularlycommonintheteenageyears. Anothermyth谬见isthatlonelinessistypicallyassociatedwithbeingalonebutitalsoaffectspeoplewhentheyaresurroundedbyothersandwellconnectedsocially.5 A.Theythinkitisusefultous. B.Sowhyarewegettinglonelier? C.Lonelinessaffectsallofusatsomepointinourlives. D.Buthowonearthcanwegetridofthisupsettingfriend? E.Lonelinessalmostaccompaniesusallthetimeandeverywhere. F.Butitiscommonlyknownthatlonelinessparticularlyaffectstheelderly. G.Thisisbecauselonelinessisaboutthequalitynotthequantityofrelationships.
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