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如图，AD，AE，BC分别切⊙O于点D，E，F，若△ABC的周长为24，则AD的长是（ ）
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如图AEADBC分别切⊙O于EDF若AD=20则△ABC的周长为．
如图△ABC中AD是边BC上的中线过点A.作AE∥BC过点D.作DE∥ABACDE交于O.点AEDE
如图已知⊙O是△ABC的外接圆AB=BCAD是BC边上的高AE是⊙O的直径.1求证AC•BC=AD•
如图已知⊙O.是△ABC的外接圆AB＝BCAD是BC边上的高AE是⊙O.的直径.过点C.作⊙O.的切
已知⊙O.为△ABC的外接圆点E.是△ABC的内心AE的延长线交BC于点F.交⊙O.于点D.1如图1
已知如图8AD是△ABC外接圆⊙O.的直径AE是△ABC的边BC上的高DF⊥BCF.为垂足.1求证B
如图AEAD和BC分别切⊙O于点EDF.如果AD＝20那么△ABC的周长为
20
30
40
50
如图AEADBC分别切⊙O.于点E.D.F.若AD=20则△ABC的周长是.
如图在△ABC中AB＝BCBE⊥AC于点E.AD⊥BC于点D.∠BAD＝45°AD与BE交于点F.连
如图AB为半圆O.的直径CD切⊙O.于点E.AD.BC分别切⊙O.于
B.两点，AD与CD相交于D.，BC与CD相交于C.，连接OD.OC，对于下列结论：①OD
2
=DE•CD；②AD+BC=CD；③OD=OC；④S.
梯形ABCD
=CD•OA；⑤∠DOC=90°；⑥若切点E.在半圆上运动（A.
两点除外），则线段AD与BC的积为定值.其中正确的个数是（ ）
A.5B.4
3
2
如图AEADBC分别切⊙O.于点E.D.F.若AD=20求△ABC的周长.
如图⊙O.分别切△ABC的三条边ABBCCA于点D.E.F.若AB=5AC=6BC=7求ADBECF
.在Rt△ABC中以AB上一点O.为圆心OB长为半径作⊙O.⊙O.与AC相切于点E.分别交ABBC于
如图AD.AE分别是⊙O.的切线D.E.为切点BC切⊙O.于F.交AD.AE于点B.C.若AD=8.
8
10
16
不能确定
如图AEADBC分别切⊙O于点EDF若AD=20则△ABC的周长为．
如图在△ABC中AB=BC以AB为直径的⊙O.分别交ACBC于点D.E.过点A.作⊙O.的切线交BC
如图⊙O.分别切△ABC的三条边ABBCCA于点D.E.F.若AB=5AC=6BC=7求ADBECF
如图已知△ABC中AB=13BC=121当∠ACB=90°时求△ABC的面积.2在1的条件下若点O.
.在Rt△ABC中以AB上一点O.为圆心OB长为半径作⊙O.⊙O.与AC相切于点E.分别交ABBC于
如图AEADBC分别切⊙O于点ED和点F若AD=8cm则△ABC的周长为cm．
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8分Forpeoplemanyotheranimalsfamilymatters.Considerhowmanyjobsgotorelatives.Orhowanantwillcruellyattackintruder入侵的antsbutrescueinjuredcloselyrelatednest﹣mates.Therearegoodevolutionaryreasonstoaidrelativesafterall.Nowitseemsfamilyfeelingsmaystirinplantsaswell. ACanadianbiologistplantedtheseedoftheideamorethanadecadeagobutmanyplantbiologistsregardeditasheretical﹣plantslackthenervoussystemsthatenableanimalstorecognizekin家族sohowcantheyknowtheirrelatives?Butwithaseriesofrecentfindingsthebeliefthatplantsreallydocarefortheirmostgeneticallyclosepeers﹣inaquietplantyway﹣istakingroot.Somespeciescontrolhowfartheirrootsspreadotherschangehowmanyflowerstheyproduceandafewtilt倾斜orshifttheirleavestominimizeshadingofneighboringplantsfavoringrelatedindividuals. Weneedtorecognizethatplantsnotonlysensewhetherit'slightordarkorifthey'vebeentouchedbutalsowhomtheyareinteractingwithsaysSusanDudleyaplantevolutionaryecologistwhoseearlyplantkinrecognitionstudiessparkedtheinterestofmanyscientists. Beyondbroadeningviewsofplantbehaviorthenewworkmayhaveapracticalside.InSeptember2018ateaminChinareportedthatriceplantedwithkingrowsbetterafindingthatsuggestedfamilytiescanbeusedtoimprovecropyields.ItseemsanytimeanyonelooksforittheyfindakineffectsaysAndreKesslerachemicalecologistatCornellUniversity. 1Whyareantsmentionedinthefirstparagraph? A.Toshowhowcruelantsaretotheirenemies. B.Tolayfoundationfortheideaofplants'familyfeelings. C.Tointroducethetopicofhowfamilymatterstoanimals. D.Toexplainwhypeopleusuallygivemorejobstotheirrelatives. 2Whichofthefollowingwordshastheclosestmeaningtotheunderlinedwordheretical? A.Indescribable. B.Understandable. C.Impossible. D.Traditional. 3Whatmaybetheplants'wayofexpressingtheircareforrelatives? A.Theystopproducingflowerstoavoidcompetition. B.Theyspreadtheirrootsfarsoastoprotecttheirpeers. C.Theycarefortheirinjuredpeersbysilentlytakingroots. D.Theymovetheirleavestosharesunlightwiththeirclosepeers. 4Whatcanbeinferredfromthetext? A.Differentplantsmustn'tbeplantedtogether. B.Cornplantedwithcorncanproducemorethanthatwithrice. C.Chinahasputtheideaintowidepracticeandachievedgreatsuccess. D.Thecloserriceisplantedwiththeirrelativesthemoretheywillproduce.
25分假设你是李华收到了正在学中文的外国朋友Peter送给你的马克吐温写的一本书TheAdventuresofTomSawyer汤姆索亚历险记作为回赠你想送一本能体现中国文化的书请给Peter写封电子邮件. 要点1.对他表达感谢和对这本书的喜欢 2.简单介绍你赠送的这本书 3.希望他了解中国文化. 注意1.词数100左右2.可适当增加细节以使行文连贯.
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