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如图，△ABC中，D、E分别为AB、AC的中点，则△ADE与△ABC的面积比为 ．
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如图等边△ABC中点D.E.分别为边ABAC的中点则∠DEC的度数为.
如图7所示△ABC△ADE与△EFG都是等边三角形D.和G.分别为AC和AE的中点若AB=4时则图
△ABC中D.E.分别为ABAC的中点若DE＝4AD＝3AE＝2则△ABC的周长为______.
如图在四面体P.﹣ABC中PA⊥平面ABCAB=3AC=4BC=5且D.E.F.分别为BCPCAB的
如图在△ABC中AB=ACAD⊥BC于D.点E.F.分别为DBDC的中点则图中共有全等三角形____
已知如图D.是△ABC的BC边的中点DE⊥ABDF⊥AC垂足分别为E.F.且DE=DF求证AB=AC
【发现问题】如图①在△ABC中分别以ABAC为斜边向△ABC外作等腰直角三角形直角的顶点分别为DE点
如图在等腰△ABC中AB＝AC点O.是底边BC的中点OD⊥ABOE⊥AC垂足分别为D.E.试说明OD
【发现问题】如图①在△ABC中分别以ABAC为斜边向△ABC的形外作等腰直角三角形直角的顶点分别为D
如图△ABC中E.G.分别为ABAC中点DE⊥ABFG⊥AC若∠BAC=1100求∠DAF.
如图△ABC中点D.E.分别为ABAC的中点连接DE线段BECD相交于点O若OD=2则OC=____
如图在△ABC中E.F.分别为ABAC的中点则△AEF与△ABC的面积之比为.
如图在Rt△ABC中∠ACB=90°D.E.分别为ABAC边上的中点连接DE将△ADE绕点E.旋转1
如图△ABC中D.E.分别为ABAC边上的中点若DE=6则BC=.
如图在△ABC中E.F.分别为ABAC的中点则△AEF与△ABC的面积之比为
如图△ABC中D.E.分别为ABAC的中点则△ADE与△ABC的面积比为.
如图D.E.F.分别为Rt△ABC中ABACBC的中点EF=4则CD=.
【发现问题】如图①在△ABC中分别以ABAC为斜边向△ABC的形外作等腰直角三角形直角的顶点分别为
如图点D.E.分别为△ABC的边AB.AC上的中点则△ADE的面积与四边形BCED的面积的比为
1：2
1：3
1：4
1：1
如图△ABC中DE分别为ABAC的中点则△ADE与△ABC的面积比为
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假定你是李华从小喜爱大熊猫一直通过有关网站关注几年前在美国动物园出生的大熊猫苏琳和她的母亲白云.现在苏琳即将过生日.请根据以下要点给动物园工作人员写一份信 内容1.自我介绍2.祝贺苏琳生日3.感谢工作人员4.索取苏琳的生日照片. 要求1.只能用5个句子表达全部内容 2.要使用多种时态 3.开头语已经为你写好. DearSir/Madam GreetingsfromChina!
下列有关叶绿体和线粒体内部分代谢活动的叙述正确的是
紫杉醇具有独特的抗肿瘤作用．研究人员从红豆杉中发现了一种具有产紫杉醇能力的内生真菌．为探究制备红豆杉内生真菌原生质体不含细胞壁的适宜pH和温度进行了如下实验①培养菌株离心收集菌丝体并用渗透压稳定剂洗涤两次②将获得的菌丝体分别置于不同pH或温度的培养液中并加入适量酶液震荡摇匀后每隔一段时间取样过滤离心用渗透压稳定剂洗涤两次后收集纯化的原生质体．③统计原生质体数量结果如下． 分析回答 1步骤②中加酶液的目的是洗涤时选用渗透压稳定剂的理由是． 2结果表明制备红豆杉内生真菌原生质体的适宜条件是． 3检验原生质体再生能力需要配制再生固体培养基培养基灭菌后需要冷却到℃左右才能用来倒平板． 4实验中将收集到的原生质体浓度为30×106个/mL培养液先稀释104倍再各取0.1mL稀释液分别均匀涂布在3个再生固体培养基上培养．一段时间后统计得到的菌落数分别为272124．则原生质体再生率能再生的原生质体数占全部原生质体的比例约为．
有一种XY型性别决定的虫媒花植物其花瓣性状由A﹣a和B﹣b两对独立遗传的基因控制其中B表达为红__为黄色Bb基因同时存在为红色有色花植株中雄性只有红色和黄色没有A基因仅有a基因时雌性植株没有花瓣而不能被昆虫辨识． 1B基因位染色体上在自然种群中控制花瓣性状的基因型共有种． 2某一橙红花植株与分别与红花植株实验一和黄花植株实验二杂交分别得F1． ①对该植株如何操作才能分别完成与红花植株实验一和黄花植株实验二杂交 ②在实验一的F1中雌性红花雌性橙花雌性无花瓣雄性红花雄性黄花＝33244则在自然条件下F2中橙花占． ③在实验二中其F1代没有无花瓣植株的产生则黄花植株实验二的基因型为． 3这种植物花色与昆虫之间的关系体现了生态系统的功能．
三孢布拉霉菌能用来生产胡萝卜素但该菌株的高产性状容易退化需要定期筛选出高产菌株研究表明菌体细胞内含有可将无色的TTC还原为红色复合物的物质且菌体细胞内该物质的含量越高还原能力越强胡萝卜素合成能力也越强．结合下列筛选菌株及提取胡萝卜素的流程图回答问题 三孢布拉霉菌→梯度稀释→涂布到含TTC的培养基上→挑取单菌落→扩大培养→收集菌丝并处理→萃取→鉴定 1胡萝卜素的提取方法有从植物中提取等等．上述流程图中提取到胡萝卜素后鉴定一般要用法．胡萝卜素能够治疗夜盲症干皮症等是因为夜盲症干皮症等疾病是由于缺少维生素A而引起的而1分子的β﹣胡萝卜素可被氧化分解成2分子．根据胡萝卜素的理化性质分析为了让胡萝卜素更容易被人体吸收炒胡萝卜时要多加些． 2流程图中将菌液涂布到含TTC的培养基上目的是筛选出合成胡萝卜素较强的菌体高产菌株含TTC的培养基属于填“选择”或“鉴别”培养基．对照组需涂布等量的以判断培养基是否被污染．挑取单菌落时若菌落周围则菌株合成胡萝卜素的能力较强． 3为了验证萃取物是否是胡萝卜素该同学将叶绿素b叶绿素a叶黄素萃取物和色素混合液含叶绿素b叶绿素a叶黄素和胡萝卜素依次点样在滤纸的12345位置如图甲所示并进行分离滤纸条上各色素带的位置为填字母时即可说明该萃取物最可能是胡萝卜素．
假如你班将举行一次英语班会主题为Howtobehealthy请你根据下面提示用英语写一篇发言稿. 注意1.字数120左右开头已给出不计入总词汇可适当发挥. 2.生词零食non﹣staplefood卫生hygiene Dearfriends.
It'sasituationyouneverwanttofindyourselfin.Youareonvacationpeacefullyenjoyingtheplanet'snaturalwonders.Then﹣﹣﹣outofnowhere﹣﹣﹣awildcreatureattacks.Inordertohelpyouwe'vecomeupwithalistoftipsforsurvivingvariousanimalencounters. Bears Bearsbehaveaggressivelywhentheyaresurprised.Yourguideswilltellyoutowearabellinordertoscareawayanybearsthatmaybenearby.Donotgonearbearcubsastheirmotherswillattackviolentlyinordertoprotectthem.Playdeadifthebearattacks. Snakes Snakeskilltheirprey猎物byslowlysqueezinguntilitcannolongerbreathe.Shouldyoufindyourselfbeingtakeninbyasnakeyouareadvisedtoremainstillasstrugglingwillpromptthesnaketosqueeze.Useonearmasprotectionforyourribsanduseyourotherarmtounwindthesnake. Sharks Avoidlyingonthewater'ssurfaceinanareaknowntobepopulatedwithsharks.Yourfiguremaylooklikeasealoranotheranimalthatiscommonpreyforsharks.Theycanfeelvibrations振动fromhundredsofmetersawaysoswimmingislikelytodrawsharkstowardsyou.Makeslowmovementsandtrytogettoshore.Fightbackifyouareattackedbyashark.Targetitseyes. Wilddogs Occasionallywilddogscanbemoreofathreatthanmostpeoplethink.Aswithbigcatsfrighteningthedogwithloudsoundsandmakingyouappearlargercanpreventapossibleattack.Ifanattackdoesoccurremainstandingandtrykickingthedogintheface. 68.Whichofthefollowingisthebesttitleofthetext? A.Dosanddon'tswhenyouareindanger. B.Sometipsforsurvivinganimalencounters. C.Howtopreventananimalattack. D.Howtohaveagoodvacation. 69.Thetextiswrittenfor. A.touristsB.swimmers.C.guidesD.drivers 70.Theunderlinedwordcubsinparagraph2refersto. A.adultbearsB.malebearsC.babybearsD.motherbears 71.Ifyouareattackedbyasharkyoushould. A.playdeadbylyingstillB.hititseyes C.kickitsnoseD.yellforhelp.
﹣﹣﹣WouldyoupleaseprovideussomeinformationabouttheearthquakeinQinghaiatthebeginningofthisyear?﹣﹣﹣Sure.It'ssaidthatitstartedtheafternoonofJanuary21st.A.for;on B.with;in C.with;on D.for;in
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