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如图,在平面直角坐标系中,以原点O为位似中心,将△ABO扩大到原来的2倍,得到△A′B′O.若点A的坐标是(1,2),则点A′的坐标是( )
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如图在平面直角坐标系中已知点
(―3,6)、
(―9,一3),以原点O.为位似中心,相似比为
,把△ABO缩小,则点A.的对应点A.′的坐标是( ) A.(―1,2) B.(―9,18)
(―9,18)或(9,―18)
(―1,2)或(1,―2)
如图在平面直角坐标系中△ABO的顶点坐标分别为A24B60O00以原点O为位似中心将△ABO缩小为原
在平面直角坐标系中已知点
(﹣4,2),
(﹣6,﹣4),以原点O.为位似中心,相似比为
,把△ABO缩小,则点A.的对应点A.′的坐标是( ) A.(﹣2,1)B.(﹣8,4)
(﹣2,1)或(2,﹣1)
(﹣8,4)或(8,﹣4)
如图在平面直角坐标系中已知点A.—36B.—9一3以原点O.为位似中心相似比为把△ABO缩小则点A.
在平面直角坐标系中已知点
(-4,2),
(-6,-4 ),以原点O.为位似中心,相似比为
,把△ABO缩小,则点A.的对应点A.'的坐标是 ( ) A.(-2,1) B.(-8,4)
(-8,4)或(8,-4)
(-2,1)或(2,-1)
在平面直角坐标系中已知点A﹣42B﹣6﹣4以原点O为位似中心相似比为把△ABO缩小则点A的对应点A′
(﹣2,1)
(﹣8,4)
(﹣8,4)或(8,﹣4)
(﹣2,1)或(2,﹣1)
如图在平面直角坐标系中点A的坐标-20△ABO是直角三角形∠AOB=60°.现将Rt△ABO绕原点O
在平面直角坐标系中已知点A.﹣42B.﹣6﹣4以原点O.为位似中心相似比为把△ABO缩小则点A.的对
如图在平面直角坐标系中A60B63画出所有以原点O为位似中心将△ABO缩小为原来的得到△CDO并写
在平面直角坐标系中.已知O.坐标原点.以点A.为旋转中心把△ABO顺时针旋转得△ACD并使BC∥轴记
在平面直角坐标系中△ABC顶点A.的坐标为32若以原点O.为位似中心画△ABC的位似图形△A′B′C
在平面直角坐标系中已知点E.-64F-3-3以原点O.为位似中心相似比为把△EFO缩小则E.点对应点
在平面直角坐标系中已知
(9,18),
(9,0)两点,以坐标原点O.为位似中心,位似比为1∶3,把线段AB缩小到线段A.′B.′,则A.′B.′的长度等于( ) A.1 B.2
3
6
如图在平面直角坐标系中以原点O为位似中心将△ABO扩大到原来的2倍得到△A′B′O.若点A的坐标是
(2,4)
(﹣1,﹣2)
(﹣2,﹣4)
(﹣2,﹣1)
在平面直角坐标系中已知A.63B.60两点以坐标原点O.为位似中心相似比为把线段AB缩小后得到线段A
在平面直角坐标系xOy中点A.B.的坐标分别为2﹣130以原点O.为位似中心把线段AB放大点B.的对
直角坐标系中已知点A﹣42B﹣2﹣2以原点O为位似中心把△ABO放大为原来的2倍则点A的对应点A'的
如图在平面直角坐标系中已知点
(―3,6)、
(―9,一3),以原点O.为位似中心,相似比为
,把△ABO缩小,则点A.的对应点A.′的坐标是( ) A.(―1,2);B.(―9,18);
(―9,18)或(9,―18);
(―1,2)或(1,―2)
在平面直角坐标系中△ABO三个顶点的坐标分别为A-24B-40O00.以原点O为位似中心把这个三角
在平面直角坐标系中已知点A.﹣42B.﹣6﹣4以原点O.为位似中心相似比为把△ABO缩小则点A.的对
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InthepalaceofRubylandtherewasathief.Nooneknewwhoitwasbuttheonlythingknownabouthimwasthathe1inthepalace. TheKingdecidedto2whoitwasandheaskedforhelpfromawisedwarfwhowasfamedforhis3.Thedwarfspentsomedaystherewatchingandlisteninguntiltherewasanother4﹣anotherruby红宝石wasstolen.Thenextdayafterbreakfastthewisedwarfmadeallthe5inhabitantsmeetuptogetherinthesameroom.Thedwarf6themallonebyone. Butsuddenlyoneofthe7begancoughingandcryingwrithingandcryingandfinallyhe8tothefloor.Thedwarfexplainedthatthefoodtheyhadjusteatenwas9andtheonlyantidote解药forthispoisonwashiddeninsidetherubythathadbeenstolenthe10night.Andheexpectedthatonlythethiefwouldbeableto11himselfbecausethepoisonwas12quickworking. Graduallythecoughsandgroansspreadaroundthewholeroomand13tookholdofallpresent.Allexceptoneperson.Afootmanquickly14overtowherehehadhiddentherubyfromwherehetooktherubyopeneditand15thestrangeliquidinsidetosavehisownlife. Infactthegardenerwasoneofthedwarf's16andthepoisonwasjustakindofpotion药⽔preparedbythedwarfwhichcouldcauseafew17painsforashortwhile.Thenthefootmanwas18bytheguardsandtakenimmediatelytocourt. TheKinggratefulgenerouslyrewardedthedwarf.Whenheaskedthedwarfwhathis19wasthedwarfsmiledandsaid:Ionlytrytogettheperson20thetruthtorevealthattruth.Anyonecandeceiveeveryonebutnoonecandeceivethemselves. 1A.took B.lived C.believed D.brought 2A.makeout B.bringout C.findout D.takeout 3A.intelligence B.strength C.height D.weight 4A.thief B.robber C.enemy D.stealing 5A.palace B.court C.country D.city 6A.helped B.asked C.comforted D.tended 7A.guards B.thieves C.gardeners D.dwarfs 8A.fell B.died C.killed D.drove 9A.polluted B.poisoned C.cleaned D.destroyed 10A.following B.dark C.previous D.warm 11A.leave B.punish C.escape D.rescue 12A.gently B.slightly C.particularly D.simply 13A.pleasure B.terror C.happiness D.worry 14A.walked B.Stepped C.ran D.moved 15A.boiled B.waved C.drew D.drank 16A.assistants B.enemies C.sons D.relatives 17A.small B.gentle C.strong D.slight 18A.treated B.beaten C.assisted D.arrested 19A.secret B.question C.benefit D.strength 20A.refusing B.approving C.objecting D.Knowing
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如图为中国古代刘徽的九章算术注中研究“勾股容方”问题的图形图中△ABC为直角三角形四边形DEFC为它的内接正方形已知BC=2AC=4在△ABC内任取一点则此点取自正方形DEFC内的概率为
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在直角坐标系xOy中直线的参数方程为t为参数0≤α<π以坐标原点为极点以x轴的非负半轴为极轴建立极坐标系曲线C的极坐标方程为ρ2﹣6ρcosθ﹣8ρsinθ+21=0已知直线l与曲线C交于不同的两点AB. 1求直线l的普通方程和曲线C的直角坐标方程 2设P12求|PA|2+|PB|2的取值范围.
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光刻胶的一种合成路线如图 已知 Ⅰ. Ⅱ. Ⅲ.RCOOH+CH≡CH→RCOOCH=CH2 回答下列问题 1A的名称是.C中所含氧官能团的名称是.C→D的反应类型是. 2B和银氨溶液反应的离子方程式为. 3D+G→光刻胶的化学方程式为. 4T是C的同分异构体T具有下列性质或特征①能发生水解反应和银镜反应②能使溴的四氯化碳褪色③属于芳香族化合物.则T的结构有种.其中核磁共振氢谱为5组峰且峰面积比为11222的结构简式为. 5根据已有知识并结合相关信息写出以CH3CH2OH为原料制备CH3CH2CH2COOH的合成路线流程图无机试剂任用.合成路线流程图示例如下CH2=CH2CH3CH2BrCH3CH2OH
已知椭圆的离心率为椭圆上的点到右焦点F的距离的最大值为3. 1求椭圆C的方程 2若椭圆C的右焦点F作倾斜角不为零的直线l与椭圆C交于两点MN设线段MN的垂直平分线在y轴上的截距为t求t的取值范围.
在长方体ABCD﹣A1B1C1D1中AB=4AD=AA1=2点P为CC1的中点则异面直线AP与C1D1所成角的正切值为
Formanycreaturestheoceanisaterrifyingplace.Severalmarineanimalshavedeclinedasaresultofoverfishingandpollution.Butcephalopods头足动物﹣atypeofinvertebrate无脊椎动物thatincludesoctopusescuttlefishandsquidhaveseenadramaticincreaseintheirnumbersoverthepast60years. ZoeDoubledayascientistattheUniversityofAdelaideinAustraliaconductedastudyofcephalopodsrecently.Shepointsoutthattheirpopulationriseisduetotheanimals'uniquetraits. Thecreaturescanchangetheircolorandbodyshape.Theyarefast﹣growingandliveforonlyoneortwoyears.ThisallowsthemtoadapttochangingenvironmentalconditionsmorequicklythanothermarinespeciesDoubledaysays. Risingseatemperaturesmaybespeedinguptheanimals'lifecycle.Theymaybegrowingfasterandproducingmoreyoung. Cephalopodsliveinalloftheworld'soceans.Theycanbefoundinwatersfromthefreezingpolarregionstothewarmtropicregions.Becausetheyadaptsoeasilytotheirenvironmenttheanimalsarecalledtheweedofthesea. Willoctopusescuttlefishandsquidtakeovertheworldoneday?Somepeoplemaywonder.AccordingtoDoubledaythatisunlikely.Theriseincephalopodpopulationscouldslowdowniftheanimalsrunoutofprey被捕食的动物andstartfeedingononeanother.Overfishingcouldalsohaveanimpactontheirnumbers. Fornowthecephalopodpopulationboomisgoodnewsforthemandsomeotherseacreatures.Increasesincephalopodpopulationscouldbenefitpredators捕食性动物suchasmarinemammalsandseabirdswhichrelyoncephalopodsforfoodDoubledaysays. 1Whathascausedthenumberofsomemarineanimalstoreduce? A.Shiptransportation. B.Globaloilproduction. C.Risingseatemperatures. D.Overfishingandpollution. 2TheunderlinedwordtraitsinParagraph2probablymeans. A.habits B.features C.hobbies D.looks 3AccordingtoDoubledaycephalopods. A.adapttotheenvironmentquickly B.changetheirshapeswithseason C.prefertoliveinthewarmwaters D.haveaverylonglifecycle 4Whichwouldbethebesttitleofthetext? A.Cephalopods B.WeedoftheSea C.Whowilltakeovertheworld? D.Theproblemsfacedbymarineanimals
已知数列按照k从小到大的顺序排列在一起构成一个新的数列{an}首次出现时为数列{an}的
设复数i是虚数单位则z的虚部为
如图在四棱锥P﹣ABCD的底面ABCD为矩形点P在底面ABCD的射影O落在AD上. 1求证平面PAB⊥平面PAD 2若OM分别是ADPB的中点且求三棱锥M﹣PDC的体积.
在△ABC中点O是BC的三等分点过点O的直线分别交ABAC或其延长线于不同的两点EF且若的最小值为则正数t的值为
已知定义在R上的函数fx满足fx+6=fx且y=fx+3为偶函数若fx在03内单调递减则下面结构正确的是
Afterdisappearingforover19yearsmeasles麻疹ismakingacomebackinAmerica.SinceJanuary2019thediseasehasinfectedmorethan700peoplemostlysmallchildrenandthenumberseemstobeincreasingdaily. Measlesisaninfectiousdiseasethattypicallybeginswithahighfevercoughrunnynoseandredwateryeyes.Manypeoplealsolosetheirappetitesandfeelsleepy.Aboutthreetofourdaysafterthesymptomsstartthepersonbreaksoutintoarash皮疹thatbeginsonthefaceatthehairlineandthenspreadstotheneckandtherestofthebody. Inhealthypeopletherecoverywhichtakesbetweentwotothreeweeksstartssoonaftertherashbegins.Howeverforabout40percentofpatients﹣mainlykidsundertheageoffiveorolderadults﹣thediseaseoftenleadstopneumonia肺炎whichifleftuntreatedcouldresultindeath. Therecentoutbreakisthoughttohavebeencausedbytravelerspickingupthevirusinacountrywherethediseaseisstillexistingandexposingittoanunvaccinated未接种的communityintheUS.InNewYorkitwascarriedbackbysomeonewhohadrecentlyvisitedIsraelwhichiscurrentlyundergoingasignificantmeasleswhileinWashingtonpatientzerowasinfectedbyatypethatiscurrentlycirculatinginEurope. TolimitthespreadofthediseasebeforeitgetsoutofhandUShealthofficialsareattemptingtoeducatecommunitieswithhighratesofunvaccinatedchildren.Theyarealsourgingadultstoconsultwiththeirphysiciansandgetinjectedifconsiderednecessarybythedoctor. Hopefullyhealthofficialsworldwidewillbeabletoconvinceparentsthatvaccinatingtheirchildrenwillprotectnotharmthem. 1Whatisthethirdparagraphmainlyabout? A.Thecausesofmeasles. B.Thesymptomsofmeasles. C.Thepossibleresultsofmeasles. D.Thecuresformeasles. 2WhydidsomepeopledevelopmeaslesinAmerica? A.Becauseitistoohotthisyear. B.Becausepeoplearetoostressed. C.Becausepollutionistooserious. D.BecausetheviruswastakentoAmerica. 3Whatdoweknowaboutmeasles? A.ItoncedisappearedinAmerica. B.Itstartswitharash. C.Itismildtoeveryone. D.Itisimpossibletocure. 4Inwhichsectionofanewspapermaythistextappear? A.Health. B.Education. C.Science. D.Entertainment.
FoodPartsYouShouldNeverThrowAwayintheGarbage PineappleCore果心 Whenyoucarveoutthecoreofapineappledon'tthrowitinthegarbage.Youcanusethepineapplecoreforallkindsofrecipesandtherearetonsofvitaminsandmineralshidingwithin.Tousethepineapplecore:cutitandaddittofruitsaladputitintosmoothies水果雪泥cutitintocubesandfreezeforlateruseorsimplyaddittowateroreventeatoimproveflavor. KiwiSkin Ifyouneverthoughtyoucouldeatkiwiinthewayyoueatapeachthinkagain.ThatskinreallyisgoodforyouandcontainsalotofvitaminCandinfactit'salsohigherinfiberthantherestofthefruit.Ofcoursethatroughuglyskinisn'tforeveryonesoifyoudon'tlikeittryaddingawholekiwitoasmoothietohidethetasteoftheskin. BananaPeel Mostofuseatthebananawithoutgivingthesoftpeelasecondthought.Here'swhythat'samistake:bananapeelcontainstryptophan色氨酸whichincreasesthehappinesshormone''tohelpwithmoodregulationandnervesystem.Thereareafewcreativewaystousethepeel.Cookorboilforatleast40minutestosoften.Youcanaddittosmoothiesstir﹣friesorsoups.Andforatreatsimplysliceandbakeabananawiththeskinon.WatermelonSkinandSeeds Thedeliciousredinsidemakesforarefreshingsnackorjuicebutyou'reabletogetsomepowerfulnutrientsintheskinandseedsaswell.Cutoutthewhitepartunderthegreenoutsideanduseitinyourcooking.IthasvitaminCandB6tokeepyouhealthy.Asfortheseedsyoucanroastthemintheoven.Thenaddthemtosaladsortonutsnacks. 1Whichofthefollowinghasalargeramountoffiberthanitsotherparts? A.Pineapplecore. B.Kiwiskin. C.Bananapeel. D.Watermelonskinandseeds. 2WhichofthefollowingstatementsisTRUE? A.Allthefoodabovecanbeaddedtosmoothies. B.Kiwiskincanberoastedintheoven. C.Bananapeelcanhelpliftpeople'smoods. D.ThegreenpartofwatermelonhasvitaminCandB6. 3Wherecanwemostprobablyreadthistext? A.Inabotanyinstruction. B.Inamedicinebrochure. C.Inafruitarian'srecipe. D.Inanutritionreport.
下列元素中生物体内含量最多的是
砷33As在周期表中与氮同主族砷及其化合物被运用在农药除草剂杀虫剂等. 1砷化氢的电子式为. 2成语“饮鸩止渴”中的“鸩”是指放了砒霜As2O3的酒.As2O3是一种两性氧化物写出As2O3溶于浓盐酸的化学方程式. 3砷的常见氧化物有As2O3和As2O5其中As2O5热稳定性差.根据图1写出As2O5分解为As2O3的热化学方程式. 4砷酸钠Na3AsO4具有氧化性298K时在100mL烧杯中加入10mL0.1mol/LNa3AsO4溶液20mL0.1mol/LKI溶液和20mL0.05mol/L硫酸溶液发生下列反应AsO43﹣无色+2I﹣+2H+⇌AsO33﹣无色+I2浅黄色+H2O△H.测得溶液中cI2与时间t的关系如图2所示溶液体积变化忽略不计. ①0~10min内I﹣的反应速率vI﹣=. ②在该条件下上述反应的平衡常数K=. ③升高温度溶液中AsO43﹣的平衡转化率减小则该反应的△H0填“大于”“小于”或“等于”. 5已知砷酸H3ASO4是三元酸有较强的氧化性. ①常温下砷酸的Ka1=6×10﹣3Ka2=1×10﹣7则NaH2AsO4溶液中cHAsO42﹣cH3AsO4填“>”“<”或“=”. ②某实验小组依据反应AsO43﹣+2H++2I﹣⇌AsO33﹣+I2+H2O设计如图3原电池探究pH对AsO43﹣氧化性的影响.测得输出电压与pH的关系如图4.则a点时盐桥中K+移动填“向左”“向右”或“不”c点时负极的电极反应为.
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