首页
试卷库
试题库
当前位置：
X题卡
>
所有题目
>
题目详情
如图，ABCD是边长为3的正方形，DE⊥平面ABCD，AF∥DE，DE＝3AF，BE与平面ABCD所成角为60°． （1）求证：AC⊥平面BDE； （2）设点M是线段BD上一个动点，试确定点M的...
查看本题答案
包含此试题的试卷
高二下学期数学《》真题及答案
点击查看
你可能感兴趣的试题
如图ABCD是边长为3的正方形DE⊥平面ABCDAF∥DEDE＝3AFBE与平面ABCD所成角为60
如图所示ABCD是正方形O.是正方形的中心PO⊥底面ABCD底面边长为aE.是PC的中点.1求证PA
正方形ABCD的边长为3点E在边CD的延长线上连接BE交边AD于F如果DE=1那么AF=.
如图ABCD是边长为3的正方形DE⊥平面ABCDAF∥DEDE=3AFBE与平面ABCD所成角为60
如图1点O.是正方形ABCD两对角线的交点分别延长OD到点G.OC到点E.使OG=2ODOE=2OC
如图1点O.是正方形ABCD两对角线的交点分别延长OD到点G.OC到点E.使OG=2ODOE=2OC
如图四棱锥P.－ABCD中PA⊥平面ABCD底面ABCD是边长为2的正方形PA＝ADF.为PD的中点
如图ABCD是边长为3的正方形平面ABCDAF//DEDE=3AFBE与平面ABCD所成的角为1求证
如图1点O是正方形ABCD两对角线的交点分别延长OD到点GOC到点E使OG=2ODOE=2OC然后以
正方形ABCD的边长为aPA⊥平面ABCDPA＝a则直线PB与平面PAC所成的角为________.
如图四棱锥P.―ABCD的底面是边长为1的正方形PA⊥底面ABCDPA=3AE⊥PD垂足为E.Ⅰ求证
如图ABCD是边长为3的正方形DE⊥平面ABCDAF∥DEDE=3AFBE与平面ABCD所成角为60
如图点E.F分别是正方形纸片ABCD的边BC.CD上一点将正方形纸片ABCD分别沿AE.AF折叠使得
如图正方形ABCD边长为2以直线AB为轴将正方形旋转一周所得圆柱从正面看所得图形的周长是______
如图ABCD是边长为3的正方形DE⊥平面ABCDAF∥DEDE=3AFBE与平面ABCD所成角为60
正方形ABCD.正方形BEFG和正方形RKPF的位置如图所示点G.在线段DK上正方形BEFG的边长为
10
12
14
16
如图正方形ABCD的边长为4点E.是正方形边上的点AE=5BF⊥AE垂足为点F.求BF的长.
如图已知正方形ABCD的边长为1连接ACBDCE平分∠ACD交BD于点E.则DE=.
若正方形ABCD的边长为4点EF在正方形ABCD的边上但不与正方形ABCD的顶点重合且∠AEF=9
如图正方形ABCD中对角线交于O.点正方形OMNQ与正方形ABCD的边长均为aDE=CF则两个正方形
热门试题
更多
sin＝
Iteachatauniversityandrecentlyhadaninterestinginteractionwithastudentwhoapproachedmydeskwithanassignment.Iwatchedashe1itfromhispocketandheldthecrumpled皱皮sheetouttome. What'sthat?Iasked.His2:Mywork. Iwasshocked.AllIcoulddowasstareatitlongenoughto3myvoice.ThenItoldhimtoredothe4andhanditbacktomeasaclean5andspotlesscopy.Asthestudent6Ipickedupthemerestanger. IfIhavesome7asateacherthenthisisit:quality.Inthelong8ofmyteachingcareerIhavegivenmystudentsgreatcreativefreedomand9manyextensionsofdeadlines.Butmy10ofqualityremainsanchoredinconcrete.IhavealwaysfeltthatshouldI11onthisoneessentialissuethenallislost. Sowhatbecameofmy12withthecrumpledpaper?Hegavemethepaperlikeasoldierpresentingsomethingtoaking13acatwhichiswhyI14him.Icalledhimback.WesatdowntogetherandI15hisdraftwhichwasdisorganized.Iexplained16.andclearlythatone'sfirsteffortisexactlythat:astart.Andwetookitfromtheremovingaparagraphdeletingthe17wordorsentenceand18grammar. Oncethosebasicthingswere19mystudentaskedArewedone?NotyetIsmiled.Onelaststep.Itoldhimtoreadhisworkoutloudandlistentohiswords.Afterhe20heloweredthepaperandlookedatmewithhisexpressionfilledwithhope. 1A.ruined B.pulled C.blocked D.harvested 2A.belief B.solution C.notice D.response 3A.repair B.recover C.raise D.recognize 4Aarrangement B.preparation C.adaptation D.assignment 5A.explicit B.flat C.long D.sharp 6A.twisted B.registered C.withdrew D.deposited 7A.complaint B.celebration C.appreciation D.attraction 8A.lesson B.distance C.course D.silence 9A.excused B.prohibited C.required D.allowed 10A.expectation B.assumption C.comprehension D.judgement 11A.burstout Bcutdown C.givein D.keepup 12A.career B.teacher C.draft D.student 13A.ratherthan B.orrather C.otherthan D.aswellas 14A.forgave B.scolded C.troubled D.influenced 15A.torn B.introduced C.examined D.selected 16Ahopefully B.specially C.strangely D.quietly 17A.difficult B.unnecessary C.valuable D.unconditional 18A.copying B.stressing C.correcting D.reviewing 19A.handled B.listed C.enjoyed D.tested 20A.demanded B.finished C.recorded D.settled
Ourteacherstriedteachingusaboutdeathduringnursingtraining.AsastudentnurseIknewIwouldseedeathinmy1.Ihadnoideaofthe2itwouldhaveonme3. ThefirstpersonIsawdiewasanelderlymanJohnwhohadbeen4forweeks.Hisheartwas5andthehealth﹣careteamwaskeepinghimcomfortableand6hissymptoms.Hehadstoppedspeakingdaysbeforebutwasstillawakeattimesandhis7whenwespoketohimwasbeautiful. WhenIcameontothe8onemorningthenightstaffsaidhehaddeteriorated恶化overnightandhad9lefttoleave.AtrainednurseandIgavehimabedbathshavedhimandchangedhissheets.ForthenextsixhoursI10hishandandtalkedtohim.Thedoctorcameinregularlyandaskedifheneededmorepainreliefbutheseemed11mostofthetime.Heonly12openedhiseyestosmileatme.Earlyintheafternoonthenursecamebackinandwewashedhisfaceand13hishair.Asshewasjustabouttoleavetheroomshestrokedhishairandsaid:OhJohnjust14.Minuteslaterhedid. Ithasbeen20yearssinceJohn'sdeath.Ihaveseen15deathsinmytimenursing.Ihaveseenstaffgofarbeyondthe16oftheirjobsto17thatapatienthasasgoodadeathaspossible.Iremembersomeoftheotherfacesbutnoneisquiteas18asJohn's.Heandtheprofessionalswhowere19himtaughtmethatit20howwetreatthosewhoaredying. 1A.life B.career C.mind D.family 2A.impact B.difference C.reflection D.affection 3A.instead B.regardless C.therefore D.however 4A.insisting B.challenging C.struggling D.recovering 5A.striking B.failing C.beating D.aging 6A.comforting B.decreasing C.disappearing D.relieving 7A.face B.eyes C.smile D.expression 8A.ward B.classroom C.hospital D.department 9A.days B.hours C.minutes D.seconds 10A.held B.reached C.hugged D.touched 11A.silent B.painful C.peaceful D.anxious 12A.frequently B.occasionally C.hardly D.easily 13A.combed B.tied C.washed D.smelt 14A.comeon B.passaway C.letgo D.goaway 15A.priceless B.constant C.considerate D.countless 16A.qualifications B.ability C.expectations D.exception 17A.pretend B.assume C.believe D.ensure 18A.beautiful B.vivid C.pale D.scary 19A.caringfor B.lookingfor C.bringingup D.cheeringup 20A.trains B.works C.influences D.matters
已知单位向量满足•＝0．若点C在∠AOB内且∠AOC＝60°mn∈R则下列式子定成立的是
假定你是李华你校将举办主题为中国书法的传统文化讲座.请给你的英国校友Eric写一封电子邮件邀请他参加.内容包括: 1.举办目的; 2.主讲人介绍; 3.听讲前的准备. 注意: 1.词数100左右; 2.可以适当增加细节以使行文连贯; 3.参考词汇:中国书法Chinesecalligraphy.
已知向量满足＝2且． 1求 2在△ABC中若求．
在△ABC中若sin2A＝sin2C则△ABC的形状是
cos570°＝
甲乙两人下棋甲获胜的概率是40%甲不输的概率为90%则甲乙二人下成和棋的概率为
IfyouliveinWashingtonD.C.orRedwoodCalif.youmayhaveglimpsedasmallboxyrobotrollingalongalocalsidewalkmindingit'sownbusinessbutattractingtheattentionofmanyacuriousonlooker.TheautonomousmachineswerepartofapilotprogramlastyearbyStarshipTechnologiesfocusedondeliveringmealsfromlocalrestaurantsindozensofcitiesaroundtheworld. TodaymorethaneverpeopleleadabusyanddiverselifeLexBayerStarship'sCEOsaidinastatementonline.Thehassleofneedingtorearrangeyourlifeforadeliverywillbecomeathingofthepast.Youdon'thavetoswitchyourworkingfromhomedayreschedulemeetingsvisitalockerdrivetoapostofficeorcontactadeliverymanallbecauseofamisseddelivery. Thepackagedeliveryserviceisnotavailabletoeveryonejustyet.Thecompanysaidit'srollingouttheserviceinMiltonKeynesEngland.Thewheeledrobotshaveatopspeedof4mphandcandetectobstaclesfromasfaras30feetaway.TherobotcanoperatethroughjustaboutanythingNickHandrickheadofoperationsforStarship'sD.C.officetoldTheWashingtonPost'sMauraJudkislastyear.Ifyouhadsomethingintheway﹣astick﹣it'sabletoclimbtheedgesofaroad. BygivingcustomerscontrolofwhendeliveriesoccurStarshipTechnologiesisofferingitsserviceasawaytobattlepackagetheft.InitsannouncementthecompanycitedstatisticsfromaWakefieldResearchPollforComcastlastyearthatfoundthat3in10Americanswholiveinhousesortownhouseshavehadpackagesstolen. Tosignupfortheservicewhichcostsalittlemorethan$10permonthcustomersneedtodownloadthecompany'sapp.CustomersthencreateaStarshipDeliveryAddressauniqueaddressinsideaStarshipfacilityinsteadofaresidencewheretheycanhavepackagessentfromplacessuchasAmazon.comOnceapackageisdeliveredtotheStarshipaddresscustomersreceiveatextthatallowsthemtoscheduleahomedeliveryviarobot. 1Whichcanbestreplacetheunderlinedwordhassleinparagraph2? A.failure B.expectation C.safety D.trouble 2Whatproblemisthedeliveryrobotfacing? A.Thereisalimittoitsservicearea. B.Ittakeslongertodeliverpackages. C.Itcoversashortdistanceeachtime. D.Itcan'tsensethebarriers20feetaway. 3Howdoesthepackagebyarobotavoidbeingstolen? A.Thecompanyshortensthedeliveryhour. B.Thepackageisdeliveredtothehousedirectly. C.Itsdeliverytimeisinthecontrolofcustomers. D.Thecustomersareinformedofitsdeliverytimeinadvance. 4WhatcanbeinferredaboutStarshipDeliveryAddressinthelastparagraph? A.Itisarealhomeaddressofthecustomers. B.Itcanarrangedeliveryrobotsforthecustomers. C.Itisacheapersolutiontothedeliveryofpackages. D.Itsendsthepackagesmainlytosomeshoppingplatforms.
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.LastyearZhangPingyupaidvisittoLondon.WorriedaboutthetimeavailableZhangPingyuhadmadealistofthesiteshewantedtosee.ItwastheTowerwhichshevisitedfirst.Fancy!Thissolidstonesquaretowerhadbeenremainedstandingforonethousandyears.Manynewbuildingshadexpandedaroundit.Thereforeitwasstillpartofaroyalpalaceandprisoncombined.TherefollowedStPaul'sCathedralbuiltaftertheterriblefireofLondonin1666.Itlookedsplendidlywhenfirstbuilt.WestminsterAbbeytoowasveryinteresting.ThenjustashecameoutoftheabbeyPingyuheardthefamoussoundoftheclockBigBenringoutthehour.ThenextdayPingyuwasleavingLondontoWindsorCastle.'PerhapsIwillseetheQueen?'shewonderedasshefallasleep.
ItiswithmixedemotionsthatIwenttotheyoungcriminalcentereveryfewmonthstogivevaccinations接种疫苗.OntheonehandIfeelluckytobeabletoprovideaservicethatmayhaveapositivehealtheffectontheresidents.ButontheotherhandIfeelasenseofsadnessanddisappointmentasIseetheprisonersbeingescorted押送byguardstothenursingunit. Mylastvisitwasverymemorable.Forsomereasontherewasalightnessintheair.MorethaneverbeforeIfeltalightnessasIspokewitheachperson.Wesharedstoriesandsmilesandfears.Eventhetoughestprisonersseemedtobesurroundedbylight.AsamotherIsawthemasnotonlyyouthbeingpunishedforcrimesbutalsoaschildrenwhohavethepotentialtochangeforthebetter.Mostofthemwantedtotalklonger!Theywerereachingouttous!Itfeltright. Therewasonemoreprisoner.Hewaslimitedtoadifferentunitinalonelycell.Wewereaskedifwewereokaygoingdownthere.Wesaidthatwewere.Twoguardsescortedusdownandwhenweenteredtheareainstanttearswelledupinmyeyes.Theareawassad.Theseguardsdidn'tsmile.Weenteredthecellandhadtomakedowithwhatwasthere. WeweredonebutIdidn'twanttoleave.Igavethe17yearoldagentletouchandsmileasIexplainedwhattodoregardingthesideeffects.AtfirsttherewasnoresponsesoIjustlookeddownathisbarefeetandthentomysupplies.IthoughtthatIhadbetterpackup.SuddenlyhelookedupatmeandsmiledbeforehesaidThanksandthenhegavemeathumbs﹣up.IsmiledbackandsaidYou'rewelcome.Takecareofyourself. Itwaswonderfultoreceiveakindresponsefromsomeonewhowasinsuchaharshplace.Aswewalkedbacktothemainentrancewedidn'tspeak.Wheretherecanbeasmilethereishope.Sometimessmilescanbeverypowerful. 1Whatcanweknowabouttheyoungintheyoungcriminalcenter? A.Theyreceivedregularmedicalservice. B.Theyweretreatedunfairly. C.Theystayedinbadconditions. D.Theywereforcedtotaketreatment. 2Whatwasspecialaboutthecenterthelasttimetheauthorwentthere? A.Shewasaskedtosharestories. B.Everyprisonerwaskindtoher. C.Theyoungpeopletalkedfreely. D.Shesensedarelaxingatmosphere. 3Whatdidtheyoungmanthinkoftheauthor? A.Hedislikedherforhersympathy. B.Hereallyappreciatedherkindness. C.Hethoughtshewouldchangehislife. D.Hethoughtshewasjustanordinarydoctor. 4Whatimpressedtheauthormostinthisstory? A.Theyoungman'ssmile. B.Themedicalcareforprisoners. C.Thepunishmenttotheprisoners. D.Thedifferencebetweentheyoungmanandothers.
手机支付也称为移动支MobilePayment是指允许移动用户使用其移动终端通常是手机对所消费的商品或服务进行账务支付的一种服务方式．继卡类支付网络支付后手机支付俨然成为新宠．某金融机构为了了解移动支付在大众中的熟知度对15﹣65岁的人群随机抽样调查调查的问题是“你会使用移动支付吗”其中回答“会”的共有100个人把这100个人按照年龄分成5组然后绘制成如图所示的频率分布表和频率分布直方图． 1求x 2从第134组中用分层抽样的方法抽取6人求第134组抽取的人数 3在2抽取的6人中再随机抽取2人求所抽取的2人来自同一个组的概率．
Thereisnobetterwaytoexperienceaplacethanthroughthelocalcuisine.Withseveralfoodfestivalshappeningacrosstheworldfindplentyofmotivationheretohelpyouyou'reyourbagsandgoonaglobalcookingexploration. MaineLobsterFestivalUS ThefestivalinRocklandMaineisnotedforitsseafood.CelebratedduringthefirstweekendofAugustforfivedaysitoffersfirst﹣classentertainmentfineartcookingcontestsandmore.Itisexpectedthatover20000pounds9072kilogramsoflobsterareconsumedduringthecourseofthefestival. OktoberfestGermany The16﹣daytraditionalbeerfestivalinMunichisthelargestofitskindintheworld.HeldinSeptemberandOctoberthe2013editionsawI.84milliongallonsofbeerserved.AwidevarietyoftraditionalGermandishesincludingroastporksausageandpotatoorbreaddumplingsarealsoavailable.In2019the186theditionwillbeginfromSept.21andlastuntiltact.6.Entryisfree. MentonLemonFestivalFrance Takingplacesince1896thisfestivalisheldinFebruaryandMarchinMentonontheFrenchRiviera.Basedonanewthemeeachyearimpressivesculpturesandfloatsaredeco﹣ratedwith140tonnesoflemonfruits.In2019thefestivalwillheheldfromFeb.16toMarch3onthethemeFantasticWorlds. ChinchillaMelonFestivalAustralia ChinchillainQueenslandisknownasthemeloncapitalofAustraliaandeveryotheryearinFebruaryitsresidentscelebratethegloriousredandjuicystickinessofwatermelonswiththisfour﹣dayfestivalwhichincludesmelonracesmelonskiingagiantmelonfoodfightandofcoursehavingyourfillofmelons.In2019thefestivalwillbeheldfromFeb. 14一17. 1Wheredoseafoodloversprefertogo? A.Munich. B.Menton. C.Chinchilla. D.Rockland. 2WhatisthemostpopularatOktoberfest? A.Bread. B.Potato. C.Pork. D.Beer. 3WhatisspecialaboutChinchillaMelonFestival? A.Itistheoldest. B.Itlaststhelongest. C.It'sheldeverytwoyears. D.IttakeplaceinAustralia'scapital.
△ABCD的内角ABC的对边分别为abc设sin2B+sin2C﹣sin2A＝sinBsinC． 1求A 2若求C．
某中学举行英语演讲比赛如图是七位评委为某位学生打出分数的茎叶图去掉一个最高分和一个最低分所剩数据的中位数和平均数分别为
如果点Psinθcosθcosθ位于第四象限则角θ是
某中学调查了某班全部45名同学参加书法社团和演讲社团的情况数据如表所示单位人 若从该班随机选取1名同学则该同学至少参加上述一个社团的概率为．
TheInterContinentalShanghaiWonderlandwhichwasbuiltintothesideofa1formalabandonedquarry采石场about20milessouthwestofShanghaihasbeenconsideredtheworld'sfirstundergroundhote1ortheworld's2lowskyscraper. Thetopfloorofthehotelislocatedatgroundlevelwitharoofcoveredingreenerywhile16floorsofthehotelarelocatedbelowground.Underwaterareanothertwofloors3guestscanobserveschoolsoffishthrougha15﹣metre﹣wideglasswindow.Apartfromthoseunderwater4roomeveryroominthehotelfeaturesabalconywithviewsofaglass﹣enclosedartificialwaterfall5rundownthequarrywalls.Thehotelisalsotakingadvantage6itslocationinsideasteep288﹣feetdeepquarryandisprovidingbungee﹣jumpingandrock﹣climbingattractionstothrill﹣seekingvisitors. Thehoteltook10yearstocompletewithtotalcostover﹩151million.Over5000peopleparticipatedinthe7constructofthehotel.ThechiefengineerontheprojectChenXiaxiangsaidhisteamregistered39patentsand8makehundredsoftechnologicalbreakthroughs.It'sbeenafightagainstgravityhesaid. Thehotel9designwitheco﹣friendlyprinciplesproducesitsownpowerheatingandlightingthrough10useofgeothermal地热的andsolarenergy.Roomsstartfrom4000Chineseyuanaround﹩576onsomeonlinehookingsites.
已知角θ的顶点与原点重合始边与x轴非负半轴重合终边过点21则cos2θ＝
某中学举行高广播体操比賽共10个队参赛为了确定出场顺序学校制作了10个出场序号签供大家抽签高一1班先抽则他们抽到的出场序号小于4的概率为
Haveyoueverwantedtoknowwhatadecoratorwasthinkingwhilechoosingmaterials?1Herearetipsyoushouldknowbeforeyoubuyplantsatthenursery. Anyplantsyoupickwillbeeasiertogrowiftheylikethespaceyou'replantingthemin.Sofirstgetagoodsenseoflight.Isthespotsunnyalldayorisitonlysunnyintheafternoon?Ifthespotdoesn'tseemuchdirectsunlookforshade﹣lovingplants.2Italsoinvitesattackfromdiseaseandpests. 3Afteraheavyraindoesitdryoutafteracoupleofdaysorstaywetforawhile?Plantsthatlikethesoilonthedrysidearerottenwhentheirrootsstaywet.Plantsthatdon'tlikeitdrywillfadeawayiftheydon'tgettodrinkenough.Knowingaboutthesoilhelpsyougrowhealthyplants. Howmuchspacedoyouhave?4Whatlooksliketheperfectplantmightheaburdenifitgrowstoobig.Youhavetoprune修剪itbackeverymonthjusttousethesidewalkorseeoutofwindows. Thelastthingyoushouldknowistoconsideryourownsparetime.Someplantsneedmorecarethanotherswhileothersneedless.5Varietieslikepurpleconeflowerforexampleneeddeadheadingtokeepproducingnewflowersandtopreventalotofyoungplants.Theygrowfinewithoutanycareinashortperiod. A.Howmuchyouwanttowater? B.Afteryouknowwhatthelightislikefocusonthesoil. C.Placingsun﹣loversbeneathatreekeepsthemfromflowering. D.Doyouwonderhowtoshoptherightplantsforyourcourtyard? E.Puttingmatureplantsinasunnyspotresultsinlargerandgreenerleaves. F.Payattentiontotheplants'maturesizeandknowwhatspaceyouhavetofill. G.Thereforeheawarehowmuchtimeyou'rewantingtospendtakingcareofthem.
假定你是李华你想邀请在中国留学的英国好友Peter观看京剧表演但Peter不在家你给他写张留言条内容要点: 1你到Peter家的目的; 2介绍京剧; 3询问什么时候方便再约时间观看. 注意: 1词数100左右; 2可以适当增加细节以使行文连贯; 3开头语和结尾语已为你写出. 参考词汇:quintessence精华精粹;ornate华丽的 DearPeter Yours LiHua.
Whilestaringoutofthewindowduringaflightnoteveryonewillthinkcarefullyaboutthequestionwhyairplaneshaveroundedwindowsratherthansquareones. Overtheyearsaerospaceengineeringhasmadehugestepsinairplanetechnologymeaningplanescancarrymorepassengersandgofaster.Theplaneshavealsochangedshapetoincreasesafety﹣includingthewindows.Ascommercialairtraveltookoffinthemid﹣20thcenturyairlinecompaniesbegantoflyathigheraltitudestolowertheircost﹣theairdensity密度isloweruptherecreatinglessdrag阻力forairplanes.Howeverhigheraltitudescamewithproblemslikethefacthumanbeingscan'treallysurviveat30000feet.Tomakethatpossiblethecabinwaschangedtoacylindrical圆柱体shapetosupportthepressureinside.Butatfirstplanebuildersleftinthestandardsquarewindowsandthisexpansionmeantdisaster.ThedeHavillandCometcameintofashioninthe1950s.Withaclosedcabinitwasabletogohigherandfasterthanotheraircraft. Howeverwherethere'sacornerthere'saweakspot.Windowshavingfourcornershavefourpotentialweakspotsmakingthemlikelytocrashunderstress﹣suchasairpressure.Bycurvingthewindowthestressthatwouldeventuallybreakthewindowcornerisdistributedandthechanceofitbreakingisreduced.Roundedshapesarealsostrongerandresistdeformation变形andcanthussurvivetheextremedifferencesinpressurebetweentheinsideandoutsideoftheaircraft. Fortunatelydesignersfiguredoutthelackofdesignprettyquick.Nowwehaveniceroundedairplanewindowsthatcanresistthepressureoftravelingaltitude.Itgivesbeingabletogazeoutofyourwindowtotheworldfrom35000feetawholenewoutlookdoesn'tit? 1Whydidairlinesaimtoflyathigheraltitudes? A.Toincreasesafetyoftheplane. B.Tohelptheplanetotakeoff. C.Tosavemoneyforlessdrag. D.Tocarrymorepassengersandgofaster. 2WhatdoestheunderlinedwordsdeHavillandCometinParagraph2referto? A.Aplanet. B.Aband. C.Anaircraft. D.Adesign. 3Whichistheadvantageoftheroundedwindow? A.Itreducesthepossibilityofbreakingup. B.Itweakensthestrengthofairpressure. C.Itincreasestheairpressure. D.Ithelpstosurvivetheextremeweather. 4Wheredoesthistextcomefrom? A.Anewspaperonsafedriving. B.Amagazineonfashiondesign. C.Awebsiteonsurvivalskills. D.Asciencebookonflying.
已知三个事件ABC两两互斥且PA＝0.3P＝0.6PC＝0.2则PA∪B∪C＝．
Haveyoueverspentanafternooninthebackyardmaybegrillingorenjoyingabasketballgamewhensuddenlyyounoticethateverythinggoesquiet?Thereisanoldphrasecalmbeforethestormoftenusedinasituation﹣aquietperiodjustbeforeagreatactivityorexcitement.Accordingtoourownexperienceweknowthereisactuallycalmbeforethestorm.Butwhatcausesthiscalm?Andisitalwayscalmbeforethestorm?Let'shearwhatscientistshavetosay. Aperiodofcalmhappensinaparticularkindofstormthesimplestkindofstorm﹣asingle﹣cellthunderstorm.Inthistypeofthunderstormthereisusuallyonlyonemainupdraftwhichiswarmdampairanddrawnfromplacesneartheground.Stormsneedwarmanddampairasfuelsotheytypicallydrawthatairinfromsurroundingenvironment.Stormscandrawintheairthatfittheirneedfromalldirections﹣evenfromthedirectioninwhichthestormistraveling. Asthewarmdampairispulledintoastormsystemitleavesalow﹣pressurevacuum真空comingafter.Therisingairmeetsthecolddryairthathasalreadyexistedinthestormcloudsthusthetemperatureofthewarmdampairdropsandthewatervapour水蒸汽initchangesintotinydropsthatareapreconditionofrain.Thesedropsaccumulateandbuildonlargerparticleslikedustuntiltheygrowlargeenoughtoformraindrops. Thiswarmdampairkeepsmovingupwardsbutitbecomescooleranddrierduringitstripthroughcloud.Whenitreachesthetopofthecloudtheairgetsspitout被挤出atthetop.Thisairissentrollingoutoverthebigthunderclouds.Fromtheretheairgoesdown.Warmanddryairisrelativelystableandonceitcoversaregionthatairinturncausesthecalmbeforeastorm. Mostthunderstormsthoughdon'tstartwithcalm.That'sbecausemostareactuallygroupsofstormswithcomplexwindpatterns.There'ssomuchairmovingupanddownstormgroupsthatthecalmbeforethestormneverhappens.Insteadbeforethestormitmightbereallywindy! 1Whichbestfitsthedescriptionofaparticularkindofstorm? A.Astormwithairdrawnfromeverydirection. B.Athunderstormwithoutstrongwinds. C.Athunderstormwithasingleshape. D.Astormfueledbymovingairfromtheground. 2WhatdoestheunderlinedworditinParagraph3referto? A.Coldanddryair. B.Warmanddampair. C.Coldanddampair. D.Warmanddryair. 3Whichdoesthewritermostlikelyagreeto? A.Presenceofthecalmreliesonstableair. B.Stormhappenswithoutairmovingupanddown. C.Thedriertheairisthebiggerthestormwillbe. D.Notallthunderstormsstartwiththecalm. 4Whatisthepassagemainlyabout? A.Causesandeffectsofaheavystorm. B.Anexplanationofthecalmbeforeastorm. C.Apersonalexperienceofaheavystorm. D.Abriefdescriptionofapeacefulstorm.
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Ʌ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. My71﹣year﹣oldgrandparunasmallfoodstandinanightmarketinmycityprovidelocalsnacksforpeopleworkingovertime.Receivingpaymentshasalwaysbeenaproblemforhimbeforemyhelp.Heoftenhadtofeelinhispocketforchangesoncoldnightswhilekeepingeyeonfoodintheoven.AfterlearningthisIhelpedhimsetupwithmobilepaymentappslikeWeChatPayandAlipay.MygrandpaiscontentwithwhichIdidforhimforabout95percentofhiscustomersnowpaywithhisphones.Mobilepaymenthasbecomeanessentialpartofoureverydaylife.Itnotonlydeepchangesthelifeofyoungpeoplebutalsoprovidesconvenientfortheelderly.
IntheUKwethrowawayabout2.5billiondisposable一次性的coffeecupseveryyear.Thebedthingisthelayerofpolyethylenethatdoesn'tletthecupleakandthelidwhichismostoftenmadeofpolystyrene.Thismakesthemabitofabarrier.Asaresultmostofthecupsendupinlandfillthoughtheyarerecyclableintheory. Butthereareeffortsunderwaytosettlethisproblem.OnecompanyBiomeBioplasticshascomeupwithafullyrecyclablecupthatusesnaturalmaterialssuchaspotatopowder.Mr.Minesitsgeneralmanagerbelievesthatthisisthefirsttimethatbioplastichasbeenusedfordisposablecupsandlidsthathavetodealwithhotliquid.Andthey'restillfullyrecyclable.AnothersolutionhasbeenputforwardbyFrugalpac.Theyhavepatentedacupwithalightly﹣attached一lacticinn.一layer.ThiscanbeeasilyseparatedduringtherecyclingandoffersamorepracticalsolutionthanchangingourcurrentrecyclinghabitssaysFrugal﹣pac'sfounderMartinMyerscough. SafiaQureshisaysIndiahasprovidedtheinspirationforhersolution.SheputsforwardthatweusereturnableandreusablecupswhicharetrackedandcollectedbyhercompanyCupClub.Theywillberesponsibleforcollectingwashingandredistributingthecleancupstoparticipatingtradesmen.OnefinalcreativeapproachcomesfromCupffee.Theyhavecombinedgrainstoformacupwhichcanbeconsumedoncethedrinkisfinished.Itcanholdacoffeeforupto40minutesandwillbiodegrade生物降解withinweeks. Whetheranyoftheseideasisaperfectfitforthisdisposableproblemonlytimewilltell.Allitmayrequireisalittlemorethinkingoutsidethebox. 1WhatdoweknowaboutthedisposablecoffeecupsintheUK? A.Fewarerecycled. B.Theyarestronglydesigned. C.Theyhavequalityproblems. D.Mostareenvironmentallyfriendly. 2WhatcanweinferaboutFrugalpac'scus? A.Theyareeasytopatent. B.Theyarepartlyrecyclable. C.Theyenjoygreatpopularity. D.Theysuittraditionalrecyclinghabits. 3InwhatwayareCupffee'scupsdifferentfromothers? A.Theyaretime﹣consumingtoproduce. B.Theycanbreakdowninstantly. C.Theyaretoeveryone'staste. D.Theycanbeeatable. 4Whatcanbeasuitabletitleforthetext? A.BadHabitsofUsingCoffeeCups B.ProblemwithCurrentCoffeeCups C.CreativeWaystoRecycleCoffeeCups D.ReasonsforProducingNew﹣styleCoffeeCups
InmanyplaceslikeBritainandItalyifyouleavethehousewithoutyourwalletyou'llbeinatoughsituationallday.ButinChinayoucanenjoyyourdayjust1asmartphone. TheotherdayIsetout2seehowfaraphonewouldgetmeinthecountry'scapital.AdmittedlyIwassurprisedtodiscoverhow3convenienceitwas. IusedmyphonetocallataxitomeetmyChinesefriendGuYu4wouldguidemetogetaroundBeijing.Wepaidforbreakfastby5scanaQRcodeonthewindowofarestaurantsellingjianbingoneofChina'smostpopularstreetbreakfasts.Mypurchasecost6yuanand6takejustafewseconds.Atanearbycoffeeshop7itownerscannedaQRcodeonmyphone.AswesippedourcoffeeGuYupaidherhouseholdwaterbill.Sheusedthesamesimpleprocesstopayotherbillsandevenherrent.Wealsopaidbyphoneformovieticketstakeoutfoodshoppingandfor8deliver. IhaveknownfromGuYuthatfromtinystreetstandstolargechains9hugenumberofpeopleacceptmobilepayment10mostthroughpopularappsAlipayandWeChat.
要得到函数y＝sin2x的图象只需将函数y＝sin2x﹣的图象
热门题库
更多
高二上学期物理
高二上学期英语
高二上学期生物
高二下学期数学
高二上学期化学
高二下学期物理
高三下学期物理
高三上学期物理
高三上学期生物
高三上学期化学
高二下学期化学
高二下学期生物
高三下学期生物
高三下学期化学
高三上学期英语
高二下学期英语
湘公网安备 43130202000226号