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一个四棱锥的侧棱长都相等，底面是正方形，其正（主）视图如图所示该四棱锥侧面积和体积分别是（ ）
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高三下学期数学《》真题及答案
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一个四棱锥的侧棱长都相等底面是正方形且其正视图为如图所示的等腰三角形则该四棱锥的体积是
一个四棱锥和一个三棱锥恰好可以拼接成一个三棱柱.这个四棱锥的底面为正方形且底面边长与各侧棱长相等这个
一个四棱锥和一个三棱锥恰好可以拼接成一个三棱柱.这个四棱锥的底面为正方形且底面边长与各侧棱长相等这个
一个四棱锥的侧棱长都相等底面是正方形其正主视图如图所示则该四棱锥侧面积和体积分别是
4
，8
4
，
4(
＋1)，
8,8
一个四棱锥的侧棱长都相等底面是正方形其正主视图如图所示该四棱锥侧面积和体积分别是
一个四棱锥和一个三棱锥恰好可以拼接成一个三棱柱.这个四棱锥的底面为正方形且底面边长与各侧棱长相等这个
一个四棱锥和一个三棱锥恰好可以拼接成一个三棱柱.这个四棱锥的底面为正方形且底面边长与各侧棱长相等这个
一个四棱锥和一个三棱锥恰好可以拼接成一个三棱柱.这个四棱锥的底面为正方形且底面边长与各侧棱长相等这个
下列说法正确的是_________. ①一个棱锥至少有四个面 ②如果四棱锥的底面是正方形那么这个四
一个四棱锥的侧棱长都相等底面是正方形其正主视图如图所示则该四棱锥侧面积和体积分别是
4
，8
4
，
4(
＋1)，
8,8
如图1所示将一个正四棱锥底面为正方形四条侧棱相等的其中四条边剪开得到图2则被剪开的四条边有可能是
PA，PB，AD，BC
PD，DC，BC，AB
PA，AD，PC，BC
PA，PB，PC，AD
一个四棱锥的侧棱长都相等底面是正方形其正视图如图所示则该四棱锥的侧面积等于
20
5
4(
＋1)
4
一个四棱锥和一个三棱锥恰好可以拼接成一个三棱柱这个四棱锥的底面为正方形且底面边长与各侧棱长相等这个三
一个四棱锥和一个三棱锥恰好可以拼接成一个三棱柱.这个四棱锥的底面为正方形且底面边长与各侧棱长相等这个
若正四棱锥的底面为水平面一个棱面为正垂面则其主视图为
前后棱面的缩小的类似形线框
反映底面实形的正方形线框
四个三角形线框
反映前后棱面实形的三角形线框
一个四棱锥和一个三棱锥恰好可以拼接成一个三棱柱.这个四棱锥的底面为正方形且底面边长与各侧棱长相等这个
判断下列语句的对错.1一个棱锥至少有四个面2如果四棱锥的底面是正方形那么这个四棱锥的四条侧棱都相等3
一个四棱锥和一个三棱锥恰好可以拼接成一个三棱柱.这个四棱锥的底面为正方形且底面边长与各侧棱长相等这个
一个四棱锥的侧棱长都相等底面是正方形其正主视图如图所示则该四棱锥的侧面积是
8
如图1在四棱锥P.﹣ABCD中PA⊥底面ABCD面ABCD为正方形E.为侧棱PD上一点F.为AB上一
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DirectionsReadthefollowingpassage.Summarizethemainideaandthemainpointsofthepassageinnomorethan60words.Useyourownwordsasfaraspossible. Smallbusinessesholdthekeytoemployedhappiness.Asthecalendarflipstoanotheryearmanyemployees'willconsiderstartingthenewyearonthehuntforanewjob. Intoday'schangingworkforceitismoreimportantthaneverforcompaniestorealizethatasalaryaloneisnolongerenoughtoattractorretainstrongemployees. AccordingtoasurveybyAflacsmallbusinessdeservearoundofapplausefortheirabilitytokeepemployeeshappy.Thereportfondthat85percentofsmall﹣businessemployeesarehappyintheircurrentjobandmorethanhalf51percentagreethatmostoforalloftheirhappinessintheircurrentjobisaresultofworkingforasmallbusiness. Nearlyaquarterofparticipants23percentstatedthatthefeelingofimportancewasthebestpartofworkingforasmallbusiness.Smallbusinesseshavetheuniqueabilitytomakeemployeesfeelappreciatedrespectedandvaluedonapersonalandprofessionallevel. Inasmall﹣businessenvironmenttherearetypicallyfewerlayersbetweennewcomersandleadership.Thistight﹣knitstructurecancreateafamily﹣likeatmospherethatallowsemployeestofeelthattheiropinionsmatterandthattheyplayasignificantroleinthebusiness'smission. Flexibilityisalsovitalincreatingemployeehappiness.Accordingtothereport30percentofrespondentsnotedthatflexibleschedulingwasthebestpartofworkingforasmallbusiness.Aworkplacethatpromoteshealthywork﹣lifebalancecancreatehappierlessstressedemployeesandcanalsoincreaseproductivity. Althoughsmallbusinessexcelatkeepingemployeeshappythereisalwaysroomforimprovement.Inasmall﹣businesscommunitymoneydoesnotseemtobetheonlymotivator.Infact65percentofsmall﹣businessemployeesindicatethatanimprovementintheirbenefitsofferingswouldmakethemhappier. Byofferingagreatbenefitsplanthanincludesvoluntarybenefitssmallbusinesscanensurethattheiremployeesareabletofindtherightbenefitstomeettheirindividualneeds.
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设函数fx=|2x+a|﹣|x﹣2|x∈Ra∈R． Ⅰ当a=﹣1时求不等式fx＞0的解集 Ⅱ若fx≥﹣1在x∈R上恒成立求实数a的取值范围．
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HotAirBalloons Thebasisofhowtheballoonworksisthatwarmerairrisesincoolerair.Thisisbecausehotairislighterthancoolairasithaslessmassperunitofvolume.Masscanbedefinedbythemeasureofhowmuchmattersomethingcontains.Theactualballoonhastobelargeasittakesalargeamountofheatedairtoliftitofftheground. Theburnerusespropanegastoheatuptheairintheenvelopetomovetheballoonoffthegroundandintotheair.Thepilotmustkeepfiringtheburneratregularintervalsthroughouttheflighttoensurethattheballooncontinuestothestable.Naturallythehotairwillnotescapefromthehotattheverybottomoftheenvelopasfirstlyhotairrisesandsecondlythefloatingpowerkeepsitmovingup. Tomovetheballoonupwardsthepilotopensupthepropanevaluewhichletsthepropaneflowtotheburnerwhichinturnfreestheflameupintotheenvelope.Itworksinmuchthesamewayasagasgrillthemoreyouopenthevalvethebiggertheflametobeattheairandthefastertheballoonrises. TheParachuteValveattheverytopoftheballooniswhatisusedtobringtheballoondowntowardstheground.Itisacircleoffabriccutoutofthetopoftheenvelopwhichiscontrolledbyaropewhichrunsdownthroughthemiddleoftheenvelopetothebasket.Ifthepilotwantstobringtheballoondownheorshesimplypullsontheropewhichwillopenthevalvelettinghotairescapedecreasingtheinnerairtemperature.Thiscoolingofaircausestheballoontoslowitsrise. Thepilotcanoperatehorizontallybychangingtheverticalpositionoftheballoonbecausethewindblowsindifferentdirectionsatdifferentaltitudes.Ifthepilotwantstomoveinaparticulardirectionheorshesimplyarisesandfallstotheappropriatelevelandrideswiththewind. 1Thepurposeofthisarticleisto. A.explainhowhotairballoonswork B.illustratewhyhotairballoonsareuseful C.describehotairballoons'structure D.informreadersabouthowhotairballoonsaremade 2WhatwouldhappeniftheParachuteValvecouldnotbereleasedafteritwasopened? A.Theinsideoftheballoonwouldcontinuetoheatup. B.Theballoonwouldclimbupmorerapidly C.Theself﹣sealingvalvewouldneedtotakeovertheroleoftheParachuteValve. D.Theballoonwouldbegintomovedownmorerapidly. 3Whichofthefollowingskillsorknowledgewouldbethemostusefultoaballoonpilot? A.Theabilitytosewthepanelsoffabrictogethertomakeaballoon. B.Anunderstandingofhowpropanegasismanufactured. C.Aknowledgeofthebackgroundofpassengerswhoaretravellingintheballoon. D.Aknowledgeofaircurrentsandwinddirectionsintheareawhereheispilotingtheballoon.
America'slatestsuperheroAustinPerinewhocallshimselfPresidentAustinisnowtakingthecountrybystorm.Butheisnotatypicalsuperhero.TwothingssethimapartHedoesn'tfighthumanenemiesbuthungerandhomelessness.Alsohe'sonlyfouryearsold. Oursuperhero'soriginstorystartedfromthedaywhenTJPerinehisfathertookAustintotheFirehouseMinistriesalocalshelterthatprovideshousingfoodandotherservicesforthehomeless.Astheydrovebythebuildingtheysawagroupof25homelessmenstandingonthestreetcorner.ThatdayAustinusedhisallowancetobuyeachmanasandwichandhandedthefoodouthimselfwithhissloganDon'tforgettoshowlove! AfterhereturnedeveryweekforfiveweeksinarowwordofAustin'skindnessspreadthroughsocialmedia.AustinandTJcouldfeed25to50peopleatatimebeforeandnowthankstocommunitysupporttheycanfeed800to2000people. ButAustinisn'tmerelyfillingstomachs.Hehasbeenimprovingthelivesofthehomelesspeoplehemeets.OnthatfirsttriptoFirehouseMinistriesTJandAustintalkedtoapoormannamedRaymont.TherespectAustinshowedforhimtouched41﹣year﹣oldRaymontwhoregainedhisconfidenceinlifeandfinallyfoundajobwiththehelpofTJ.Allthatwasmadepossiblebecausealittleboytookthetimetocare. Austin'spassionhasbecomehisfamily'scalling.AfterraisingmoneythroughaGoFundMepageAudreyTJ'smotherestablishedthenonprofitShowLoveFoundationdedicatedtofightinghomelessness.ShenowservesaspresidentandTJoverseespublicrelationsforthefoundationfulltime.Theyoffermedicalandmentalhealthcareaspreventivestepsagainsthomelessness. AsforPresidentAustinhecontinuestogiveoutfoodsmilesandhisinspirationalmessageoflove.ItmakesmefeellikeI'msavingthedayhesaidproudly. 1WhyhasAustinbecomewell﹣knowntotheentirecountry? A.Hehassuperpowertofillthestomachsofthehomeless. B.Hefightshungerandhomelessnessatsuchayoungage. C.Hehasremovedthepovertyofthelocalcommunity. D.Hehaschosenanimpressiveanduniquename. 2WhichofthefollowingcanreplacetheunderlinedworddedicatedinParagraph5? A.Exposed. B.Opposed. C.Devoted. D.Addicted. 3WhydoestheauthorintroducetheexampleofRaymontinParagraph4? A.ToshowAustin'spositiveinfluence. B.Topersuadepeopletoliveofftheirown. C.ToprovethepersonalabilityofAustin'sfather. D.Todescribethedifficultsituationofpoorpeople. 4Whatistheauthor'sattitudetowardswhatAustindoes? A.Sympathetic. B.Humorous. C.Approving. D.Considerate.
已知集合A={x∈Z|0＜x＜4}B={x|x+1x﹣2＜0}则A∩B=
“微信运动”是手机APP推出的多款健康运动软件中的一款大学生M的微信好友中有400位好友参与了“微信运动”．他随机抽取了40位参与“微信运动”的微信好友女20人男20人在某天的走路步数经统计其中女性好友走路的步数情况可分为五个类别A0～2000步说明“0～2000”表示大于或等于0小于2000以下同理B2000～5000步C5000～8000步D8000～10000步E10000～12000步且ABC三种类别的人数比例为143将统计结果绘制如图所示的柱形图男性好友走路的步数数据绘制如图所示的频率分布直方图． Ⅰ若以大学生M抽取的微信好友在该天行走步数的频率分布作为参与“微信运动”的所有微信好友每天走路步数的概率分布试估计大学生M的参与“微信运动”的400位微信好友中每天走路步数在2000～8000的人数 Ⅱ若在大学生M该天抽取的步数在8000～10000的微信好友中按男女比例分层抽取6人进行身体状况调查然后再从这6位微信好友中随机抽取2人进行采访求其中至少有一位女性微信好友被采访的概率．
KeepingTheTapsRunninginThirstyCities Watercovers71%ofEarth'ssurfaceyetonly2%ofitisaccessibleasasourceoffreshwater.1onthislimitedresourcesisrisingatrendlikelytocontinue. Itisimportanttorecognizethatitisnotjustcityresidentswho2water.Agricultureindustryandtourismoftenrequiremorewaterthanthemunicipalwatersupply.Globally70%offreshwateris3foragriculturebutlocallyinheavilyirrigated灌溉areasthiscanincreateto90%.Ahealthyenvironmentalsorequiresfreshwaterandthequalityofavailablewaterisasimportantasits4. Waterstressisnotalwayscausedbyphysicalshortagesindryareas.5forwaterresourcesbetweendifferentuserswithinrivercatchmentsorbasinscanalsobeacause. Everythirstycityoperateswithinitsowncontext6tothechallengeofprovidingadequatewatersupplies.CapeTown7hasfacedthreeyearsofdroughtduringwhichwinterrainsfailedtomaterialize.Attheendofthe2017rainyseasonthecityfacedthe8ofitsdamsrunningdryduring2018.Thedamswereonly37%full﹣inthesameweekfouryearsbeforetheywerefulltothetop.InJanuary2018itwas9thatCapeTownwouldreachDayZerowhenitwouldbeforcedtoturnoffthetapsinApril.Thiswasdespitethecityreducingitswaterusebymorethanhalffrom1.2billionlitresadayin2015tofewerthan600millionlitresandworking10withindustryandagriculturetoreducedemand. OnFebruary1theauthoritiesputinplaceastrictlimitof50litresofwaterperpersonperday.11inBritainthisisconsideredenoughforafive﹣minuteshowerofhalfawashingmachinecycleonfullload. Inadditionabanwasplacedonusing12waterforgardenswatermanagementdeviceswereinstalledathouseholdwithahighwateruseandthewaterpressurewasreducedtocutdemandandleaks.Atthesamethecitylaunchedamedia13tochangehabitsandintroducedhigherduties.Thisisnotwithoutitscostsagricultureandtourismbothsignificantareasofemploymenthave14.Itisaclassicexampleoftheproblemofwatereconomics﹣thecostofwaterislowbutthecostofalackofwaterisveryhigh. CrisessuchastheCapeTowndroughtareindangerofbecomingthenewnorm.The15ofDayZeromustserveasawake﹣upcallforcitiesacrosstheworldtodevelopcost﹣effectivewatermanagementstrategiestocopewithanuncertainfuture. 1A.Impact B.Pressure C.Impression D.Observation 2A.recycle B.waste C.consume D.apply 3A.restored B.abstracted C.separated D.preserved 4A.change B.source C.origin D.volume 5A.Competition B.Protection C.Construction D.Regulation 6A.contributing B.regarding C.responding D.referring 7A.inaddition B.forexample C.onthecontrary D.asaresult 8A.prospect B.illustration C.symptom D.security 9A.reported B.presented C.predicted D.explained 10A.respectively B.increasingly C.restrictively D.extensively 11A.Bycomparison B.Inotherwords C.Tooursurprise D.What'smore 12A.feasible B.drinkable C.inevitable D.influential 13A.campaign B.statement C.presentation D.advertisement 14A.invaded B.liberated C.suffered D.proceeded 15A.change B.theory C.record D.threat
若则cos2α的值是．
Herearesomebestsellersof2018atAmazon. Thecar Fourteen﹣year﹣oldTerry'sparentsneverpayhimmuchattention.Sowhentheybothdisappearafteroneoftheirall﹣too﹣frequentargumentsTerryisn'texactlyeagerforthemtocomehome.Onhisownhefixesanabandonedcar.Thoughhedoesn'tknowmuchaboutdrivinghegetsbehindthewheelandheadswestwiththeintentionofvisitinganuncleinOregon.It'sanexcitingandsometimesdangerousjourney.AlongthewayhelearnsalotaboutpeopleaboutAmerica﹣﹣andmostimportantlyabouthimself. TheRunningDream Jessicathinksherlifeisoverwhenshelosesaleginacaraccident. Asshestrugglestocopewithherprosthesis义肢andmanyotherdifficultiesJessicadevelopsacloserelationshipwithRosaagirlwhohasacancerandseesrightintoJessica'sheart. WiththesupportoffamilyfriendsacoachandherteammatesJessicaisabletorunagain.Butthat'snotenoughforhernow.Shedoesn'tjustwanttocrossfinishlinesherself﹣shewantstotakeRosawithher. HaveaNewTeenagerbyFriday Doyouknowthisperson? Hisbedroomlookslikeagarbagedump. Shechangesclothesthreetimesbeforebreakfast. Itseemsthathe/sheneveragreeswithyou. Congratulations!Youhaveateenagerinyourhome.Butyouneedn'tfeelhelpless.Infactyou'rejustfivedaysawayfromyourteenagerasking.WhatcanIdotohelp?InternationallyrecognizedfamilyexpertDr.KevinLemanwillhelpyougetrealresults﹣reallyfast. BoyRobot Seventeen﹣year﹣oldIsaakdiscoversthetruthabouthisoriginagovernment﹣madehuman.Butadeadlymilitaryforceistryingtokillhim.HeandtheotherRobotscanonlyfindprotectionfromtheUnderground﹣asecretnetworkofRobotsandhumansworkingtogethertoensureacoexistentfuture.Isaakmustdecidewhethertoholdontohishumanityandfacepossibledeathortoembracehistruenatureinordertosurvive. Ifyouareinterestedinanyofthebooksclickhereforfurtherinformation https∥www.amazon.com/. 1Whichbookisasciencefiction? A.TheCar. B.TheRunningDream. C.HaveaNewTeenagerbyFriday. D.BoyRobot. 2Whichofthefollowingisn'tconveyedinTheRunningDream? A.Friendship. B.Modesty. C.Bravery. D.Determination. 3WhoisthebookHaveaNewTeenagerbyFridayintendedfor? A.Experts. B.Teenagers. C.Parents. D.Teachers.
在直角坐标系xOy中以坐标原点O为极点x轴的正半轴为极轴建立极坐标系已知曲线C1的极坐标方程为ρ=2sinθ直线l的参数方程为t为参数． Ⅰ求曲线C1的参数方程和直线l的直角坐标方程 Ⅱ设D为曲线C1上在第二象限内的点且在点D处的切线与直线l平行求点D的直角坐标．
已知数列{an}的前n项和Sn=n2﹣5nn∈N+． Ⅰ求数列{an}的通项公式 Ⅱ求数列{}的前n项和Tn．
Thekoalaisanunusualcreature.NativetoAustraliaandabitbiggerthanarabbititspendsmostofitstimeineucalyptustrees桉树feedingonleavesthatarepoisonoustonearlyeveryotheranimalontheplanet. Thekoalasleepsabout22hoursadayandspendstheremainderofitstimeeatingandresting.Itmightspend10minutesadaymovingexpertssayusuallyfromonetreetoanother.Ithasasoftpadattheendofitsspineandextrathickfuronitsrearendtomaketheeffortofsittingmorecomfortable. ThreatsandprotectivemeasuresTheuniquelifestyleofthekoalahashelpeditprosperbuttodaythecuteandiconiccreatureisfacingthreatsfromhabitatlossdiseaseandachangingclimate. Koalapopulationsareexpectedtodeclineby50percentinthenext20yearsaccordingtotheAustralianMuseum. Tohelpprotecttheseanimalswhichbringinanestimated＄1.1billiontoAustraliaeachyearthroughkoala﹣relatedtourismaninternationalteamofresearchershaspublishedthefirstcompletegenome基因组ofthekoala. Theirhopeisthatthekeystothemarsupial's有袋动物long﹣termsurvivalmightbeplantedinitsgeneticcode. Theultimategoalisthatwewon'thaveto…rescuethemfromtheedgeofextinctionsaidRebeccaJohnsonoftheAustralianMuseumResearchInstituteinSydneywholedthework. Nowwehaveareallygoodunderstandingofthekoalagenomeandweareinafantasticpositiontousethatknowledgetohelpusmanagethem. Earlyfindings Anelementaryanalysisofthekoala'sgenomepublishedinNatureGeneticshasalreadyyieldedsomeinterestingfindings. Forexampletheauthorsfoundthatcomparedtoothermammalsthekoala'sDNAincludesanexpansioninthenumberofgenesthatencodeforenzymesinvolvedinanti﹣poison.Thatallowsthemtohaveadietthatdependsalmostentirelyoneucalyplusleaveswhichareunusuallyhighinpoison.Howeveritalsomeansthatkoalasmetabolize代谢medicineslikeanti﹣chlamydiaantibioticsfasterthanotheranimals. Thekoalagenomealsorevealedwhykoalasaresuchfamouslypickyeaters.Theyareknowntoconsumeleavesfromjust20ofAustralia's60knowneucalyplusspecies.Andevenwhentheyareinoneoftheirpreferredtreeskoalastakeleafselectionveryseriously. Informationwaitingtobediscovered Johnsonsaidthattheinformationencodedinthekoala'sDNAisalreadybeingincludedinmanagementstrategiesbyconservationgroups.Howevershesaidthefindingsdescribedinthenewpaperrepresenttheearlystagesofwhatcanbegleamedfromthemarsupial'sgenome. ThedataispublicandIwouldloveforanyonetostartminingitandseewhatotheramazingthingstheycanfindshesaid.Onceyouhaveagenomeofthisqualitythesky'sthelimitwithwhatyoucandowithit. 1Whatcanbeconcludedfromthepassage? A.TheresearchontheKoala'sDNAhaspreventeditsextinctionsuccessfully. B.ScientistsaretryingtorescueKoalasbyprovidingmoreeucalyptusleaves. C.Koala'sextinctionisbeingcontrolledeffectivelyinAustralia. D.ScientistsaretryingtofindawaybasedonKoala'sgenetosavethem. 2AccordingtothepassagewhichofthefollowingisTRUE? A.Koalascandigestpoisonousleavesthankstotheirgene. B.Koalasareparticularaboutleavesbecauseoftheirtaste. C.Koalasarebeingextinctjustduetohuman'sactivities. D.Koalaswillmovetoothercontinentsinordertosurvive. 3Thesky'sthelimitinthelastsentencemostprobablymeans. A.Theskyistherestriction B.Theskyistoohightoreach C.Thereisnolimit D.Thereisnopossibility 4Thepassageismainlyabout. A.Koala﹣aSpecialCreatureinAustralia B.scientificresearchonKoalas C.scientificeffortstosavetheKoalas D.Koala'sCharactersandPreference
NowhereToHideWhatMachinesCanTellFromYourFace Thehumanfaceisaremarkablepieceofwork.1.Soistheface'sabilitytosendemotionalsignalswhetherthroughtheunconsciousshameorthetrickofafalsesmile.Peoplespendmuchoftheirwakinglivesintheofficeandthecourtroomaswellasthebarandthebedroomreadingfacesforsignsofattractionhostilitytrustanddeceit.Theyalsospendplentyoftimetryingtohidetheirfeelingsintentionsornature. 2.InAmericafacialrecognitionisusedbychurchestotrackworshippers'attendanceinBritainbyretailerstospotpastshoplifters.ThisyearWelshpoliceusedittoarrestasuspectoutsideafootballgame.InChinaitconfirmstheidentitiesofride﹣hailingdriverspermitstouriststoenterattractionsandletspeoplepayforthingswithasmile.Apple'snewiPhoneisexpectedtouseittounlockthehomescreen Setagainsthumanskillssuchapplicationsmightseemenhancive.Somebreakthroughssuchasflightortheinternetobviouslytransformhumanabilities.3.Althoughfacesarepeculiartoindividualstheyarealsopublicsotechnologydoesnotatfirstsightintrudeonsomethingthatisprivate.Andyettheabilitytorecordstoreandanalyseimagesoffacescheaplyquicklyandonavastscalepromisesonedaytobringaboutfundamentalchangestonotionsofprivacyfairnessandtrust. 4.Maskingtruefeelingshelpsfixthewheelsofdailylife.Ifyourpartnercanspoteveryprohibitedyawnandyourbosseveryhintofannoyancemarriagesandworkingrelationshipswillbemoretruthfulbutlessharmonious.Thebasisofsocialinteractionsmightchangetoofromasetofcommitmentsfoundedontrusttocalculationsofriskandrewardderivedfromtheinformationacomputerattachestosomeone'sface.Relationshipsmightbecomemorereasonablebutalsotransactional.
执行如图的程序框图则输出的S的值是
若函数fx=xlnx﹣x3+x2﹣ax有两个不同的零点则实数a的取值范围是
Whenwasthelasttimethatyoudialedaphonenumberfrommemory?Itprobablydependsonhowlongyou'vebeenusing1likeacellphone.Whilesomegenerationscanrecallthedaysofmemorizingphonenumbersit'spossiblethatmembersofGenerationZhaveneverhadtorememberasingle2.Whyisthis?Becausesmartphonesofferquickandconvenientwaysforstoringand3information.Thereisnoneedtomemorizeanything.Butthisisn'twithoutconsequence.Asdigitaldevicesdevelopmoreandmoreusers'heavyrelianceonthemmaybehavingdisablingeffects.Digitaldementia失智isthetermbeingusedbymedicalprofessionalstoidentifysomeoftheseeffects. SomeprofessionalslikeJimKwikanexpertinmemoryimprovementandoptimalbrainperformancearetakingacloserlookatthiseffect.Kwikdescribesdigitaldementialikethis…we're4ourbrainstooursmartdevices.We'resoreliantonoursmartphonesthatoursmartphonesaremakingusstupid.Asmedicalstudieschartthedeclineinmemoryandcognitiveskillsamongsmartphoneusersaconnectionismadebetweensymptoms5withdementia. Theseriousnessofoverusebecomes6whenyouconsiderjusthowyoungsmartphoneusersarebecoming.AuthorandspeakerSimonSinekpointsoutthatyoungmindsArenotreadyforit!Theirmindscannotcopewiththedopamine多巴胺.Consequentlytheoverstimulationofscreensandsoundsleadto7moreoftenthannot.Sonowparentsteachersandmanagersareaskinghowtohandletheinflux汇集ofyoungpeoplewiththiskindofaddiction. ●Firstmonitoryourcellphoneuse.KeepdownloadingapplicationslikeForestorChecky.Thencutbackonany8usage.Setaspecificgoalofhowmuchyouthinkyoushoulduseyourphone. ●Determine9areasforcellphoneuse.Forexamplewhileyou'reathomeonlyallowyourselftocheckyourphonesomewherelikeahomeoffice.Thiswaythetimeinbetweentasksisn't10filledwithstaringatyourscreen.
如图三棱柱ABC﹣A1B1C1中AB=AA1=AC=2∠BAC=∠A1AC=45°∠BAA1=60°F为棱AC的中点E在棱BC上且BE=2EC． Ⅰ求证A1B∥平面EFC1 Ⅱ求三棱柱ABC﹣A1B1C1的体积．
已知函数fx=lnx+ax2﹣xx＞0a∈R． Ⅰ讨论函数fx的单调性 Ⅱ求证当a≤0时曲线y=fx上任意一点处的切线与该曲线只有一个公共点．
JustHowBuggyisYourPhone? Whatiteminyourhomecrawlswiththemostgerms?Ifyousay1toiletseatyou'rewrong.Kitchenspongestopthelist.Butcellphonesareprettydirtytoo.Theycontainaround10timesasmanygermsastoiletseats.Peopletouchtheirphoneslaptopsandotherdigitaldevicesalldaylongyetrarelycleanthem. Inoneincidentathiefpaidaterriblepriceforstealingagermycellphone.HestoleitfromahospitalinUgandaduringawidespreadofthedeadlydiseaseEbola.Thephone'sownerreportedthetheftbefore2diefromthedisease.Soonthethiefbeganshowingsymptomsandfinally3confesstothecrime. 4inthatunusualcaseacellphonecarrieddangerousbacterianotallgermsarebad.Mostcausenoharm.Infacttheycouldprovidehelpfulinformation.Lookatthesurfaceofyourphonecarefully.Doyouseesomedirtymars?That'sallyousaysmicrobialecologistJarradHampton﹣Marcell.That'sbiologicalinformation. Itturnsoutthatthetypesofgermsthatyouapplyalloveryourphoneortabletaredifferentfrom5ofyourfriendsandfamily.They'relikeafingerprintthatcouldidentifyyou.Somedayinthefutureinvestigatorsmayusethesemicrobialfingerprintstosolvecrimes.Phonesanddigitaldevicesmaybeoneofthebestplacestolookforbuggyclues. Ina2017studyresearcherssampledarangeofsurfacesin22participants'homes6countertopsandfloorstocomputerkeyboardsandmice.Thentheytriedtomatchthemicrobialfingerprintsoneachobjecttoitsowner.Theofficeequipmentwaseasiesttomatchtoitsowner.Inan7earlystudyadifferentgroupofresearchersfoundthattheycouldusemicrobialfingerprintstoidentifythepersonwho8useacomputerkeyboardevenafterthekeyboardsatuntouchedfortwoweeksatroomtemperature. Onedaymicrobialsignaturesmightshow9peoplehavegoneandwhattheyhavetouched.Theycouldprove10anunmarkeddeviceisyours.Sosureyourphoneisprettygermy.Doesthatinspireyouordoesitjustbotheryou?
各项为正数的等比数列{an}中a2与a10的等比中项为则log3a4+log3a8=．
Manypeopleprefereatingoutinsteadofcookingathome.Achangeappearstobetakingplacethoughandmillennialsareleadingtheway.AccordingtoonesurveymoreyoungpeoplearestartingtocookathomeforthreebasicreasonsTheycansavemoneyeathealthyandwastelessfood. PopularTVchefsarealsogettingmillennialsexcitedaboutlearningsomebasiccookingskills.Manymillennialsviewcookingasaformofentertainmentandself﹣expression.TheyproudlypostpicturesoftheircookingcreationsonFacebookorInstagramandinvitefriendsovertosharethecookingexperience. Manymillennialshavealsofoundwaystoavoidwastingfood.Afterroastingachickentheyputtheleftoverbonesintheirfreezerinsteadofthegarbagecan.Latertheyusethebonestomakechickenstockwhichisanimportantingredientinmanydishes. Theyalsohatethrowingoutfruitthat'stooold.Toavoidthatsituationtheybakeripefruitlikeberriesandbananasfor15minutesat175degreesC.Thentheyfreezeitovernight.Afterthattheyplacethefruitinplasticbagsandstoreittheirfreezerforlateruse. Nowanymillennialsonlyeatatrestaurantsthathaveexcellentfood﹣wastepolicies.Theseservantsuseeverypartofthevegetablestheybuyincludingtheirstemsandrootsindishes.Theyalsousebeefchickenandporkbonestomaketheirownstock. Millennialsalsoreducefoodwastebyonlybuyingwhattheyrequire.Beforegoingtoamarkettheywritedownwhattheyneedanddon'tbuyanythingelse.Theywaytheywon'tpurchasemorefoodthantheycanconsume. 1Whatisthemainsubjectofthisarticle? A.Acookingtrendthathasattractedmillennials. B.Aplanthatmillennialshavefordonatingfood. C.Anovelcookingtechniquethatmillennialslike. D.Afoodproductionsystemfavoredbymillennials. 2Whatdomillennialswithfruitbeforefreezingit? A.Mixitwithotheringredientsinabowl. B.Carefullyremovetheskinandseedsfromit. C.Useasharpknifetochopitupintopieces. D.Putitinanovenatthepropertemperature. 3Accordingtothisarticlewhendomillennialsmakecarefulchoices? A.Whentheydineouttogether B.Wheytheyvoteforcandidates C.Whentheychooseanemployer D.Whentheyplantanewgarden 4Accordingtothisarticlehowdomillennialsavoidpurchasingtoomuchfood? A.Theyselectsmallcansandpackages. B.Theyprepareapracticalshoppinglist. C.Theyleavetheircreditcardsathome. D.Theyweighproducebeforebuyingit.
实数xy满足约束条件则z=2x﹣y的最小值是
军训时甲乙两名同学进行射击比赛共比赛10场每场比赛各射击四次且用每场击中环数之和作为该场比赛的成绩．数学老师将甲乙两名同学的10场比赛成绩绘成如图所示的茎叶图并给出下列4个结论1甲的平均成绩比乙的平均成绩高2甲的成绩的极差是293乙的成绩的众数是214乙的成绩的中位数是18．则这4个结论中正确结论的个数为
已知点M21在椭圆C上AB是长轴的两个端点且．Ⅰ求椭圆C的标准方程Ⅱ已知点E10过点M21的直线l与椭圆的另一个交点为N若点E总在以MN为直径的圆内求直线l的斜率的取值范围．
在三棱锥P﹣ABC中已知PA=AB=AC∠BAC=∠PAC点DE分别为棱BCPC的中点则下列结论正确的是
DirectionsWriteanEnglishcompositionin120﹣150wordsaccordingtotheinstructionsgivenbelowinChinese. 假设你是明启中学高三学生卢平你的网友王磊近日就学习时如何记好笔记发邮件向你求教请给他回复一封电子邮件邮件必须包括以下内容 ●描述两到三个不同的笔记类型及其特征 ●如何记好笔记的建议 注意中文请不要出现真实的校名人名
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