四边形解题技巧

校长为学校学生道路交通安全工作第一责任人，负责校（园）内的道路交通安全管理工作和学生出行的道路交通安全教育，以及学生春(秋)游和其他教育教学活动的道路交通安全管理工作centerpinchecksandanchoringtheinnercylinder.AccordingtoWhilecouplingalignmentshouldkeepoiloutofcavityandlocatetherotoraxisneckraisedarewithintheprescribedlimits,thereshouldbenogaps,Horn,HornandHorn0.05mmfeelergaugesfitinto.Centercoupling,condenserwaterfillingandwater-filledaccordingtofactoryrequirement.ForcouplingthreesupportedrotorCenter,themouthunderthecouplingbetweenthevalueshouldbeasstipulatedinthemanufacturer,usually0.15~0.25mm.Inthecaseofcouplingconnection,ifpossible,liftingonlyonebearingendofthesupportbearingoftherotor,removethebearing,fittedwithspecialtilesandspecialliftingtools,discrotors,checkthejournalfluttertile,shouldgenerallybelessthan0.10MM.Whenthecouplingsandrotorcomeswhenthereisaconflict,thecouplingCentreshallprevail.6.4.5.2.2shaftlookingfor:...6.4.5.3.Provisionalboltconfirmedthepositioningoftherotorsize,aswellasthecouplingbetweentheadjustmentshimthicknessaccuracy,drawingstomeetthetechnicalrequirements.Plane,cylindricalandcleanthecouplingboltholesshouldbecleanandwithoutburrs,scrapironandgrease-free,relativepositionofthecouplingaccordingtothedrawingrequirementsare.Couplingtopscrews,rounddistanceapart,indicatorstomonitormovementoftheaircraft,itsvalueisallowedtopassthevalueaxismoving,mountedadjustmentpads,notepadsinstallationdirectionguidepincouplingwithprocessendclosed.Thebackwheelsslowlytightened,when2mmorso,withstandardwhitebarswheretwobackwheelboltholemeasurementaboveandbelow,confirmtwobackwheelboltholeconcentricity.Then,thesymmetricalhorizontalmounttwotemporaryboltstightened,attentiontomonitordialindicator,theninstallthesymmetricaltemporarybolts,thistimesitesslowlymovingrotor,inthemeasuredcircumferenceof8equalpartsbackwheelrimrock,eachmeasuringrelativechangesinvalueshouldbelessthan0.02mm.6.4.5.4couplingreamedandpairedboltreamingdiereamer,adjustablereamers,boringmill,inseveralways.6.4.5.4.1Generalrequirementsbeforereamingorboring,四边形解题技巧一、平行四边形应用举例平行四边形具有对边平行且相等、对角相等、对角线互相平分等性质，它们在计算、证明中都有广泛的应用，现举例说明．1．求角的度数例1如图，ABCD中．AD=2AB，点E、A、B、F在一条直线上，且EA＝AB＝BF，求∠DOC的度数．例2（2007·河北）如图，若ABCD与EBCF关于BC所在直线对称，∠ABE=90°，则∠F=______．2．求线段的长例3如图，在四边形ABCD中，AB＝6，BC＝8，∠A=120°，∠B＝60°，∠BCD＝∠150°，求AD的长．例4(2006·河北)如图，在DABCD中，AD＝5，AB=3，AE平分∠BAD交BC边于点E，则线段BE、EC的长度分别为()A．2和3B．3和2C．4和1D．1和43．求周长例5(2006·日照)如图，在ABCD中，AE⊥BC于E，AF⊥CD于F，∠EAF=45°，且AE+AF=22，求ABCD的周长．4．求第三边的取值范围例6(2006·双柏)如图，在ABCD中，对角线AC和BD相交于点0，如果AC=12，BD=10，校长为学校学生道路交通安全工作第一责任人，负责校（园）内的道路交通安全管理工作和学生出行的道路交通安全教育，以及学生春(秋)游和其他教育教学活动的道路交通安全管理工作centerpinchecksandanchoringtheinnercylinder.AccordingtoWhilecouplingalignmentshouldkeepoiloutofcavityandlocatetherotoraxisneckraisedarewithintheprescribedlimits,thereshouldbenogaps,Horn,HornandHorn0.05mmfeelergaugesfitinto.Centercoupling,condenserwaterfillingandwater-filledaccordingtofactoryrequirement.ForcouplingthreesupportedrotorCenter,themouthunderthecouplingbetweenthevalueshouldbeasstipulatedinthemanufacturer,usually0.15~0.25mm.Inthecaseofcouplingconnection,ifpossible,liftingonlyonebearingendofthesupportbearingoftherotor,removethebearing,fittedwithspecialtilesandspecialliftingtools,discrotors,checkthejournalfluttertile,shouldgenerallybelessthan0.10MM.Whenthecouplingsandrotorcomeswhenthereisaconflict,thecouplingCentreshallprevail.6.4.5.2.2shaftlookingfor:...6.4.5.3.Provisionalboltconfirmedthepositioningoftherotorsize,aswellasthecouplingbetweentheadjustmentshimthicknessaccuracy,drawingstomeetthetechnicalrequirements.Plane,cylindricalandcleanthecouplingboltholesshouldbecleanandwithoutburrs,scrapironandgrease-free,relativepositionofthecouplingaccordingtothedrawingrequirementsare.Couplingtopscrews,rounddistanceapart,indicatorstomonitormovementoftheaircraft,itsvalueisallowedtopassthevalueaxismoving,mountedadjustmentpads,notepadsinstallationdirectionguidepincouplingwithprocessendclosed.Thebackwheelsslowlytightened,when2mmorso,withstandardwhitebarswheretwobackwheelboltholemeasurementaboveandbelow,confirmtwobackwheelboltholeconcentricity.Then,thesymmetricalhorizontalmounttwotemporaryboltstightened,attentiontomonitordialindicator,theninstallthesymmetricaltemporarybolts,thistimesitesslowlymovingrotor,inthemeasuredcircumferenceof8equalpartsbackwheelrimrock,eachmeasuringrelativechangesinvalueshouldbelessthan0.02mm.6.4.5.4couplingreamedandpairedboltreamingdiereamer,adjustablereamers,boringmill,inseveralways.6.4.5.4.1Generalrequirementsbeforereamingorboring,2AB=m，那么m的取值范围是()A．10m12B．2m22C．lmllD．5m65．综合计算题例7如图,ABCD的周长为26310，BC的长为35，AE⊥BC于E，AF⊥DC，垂足为DC延长线上的点F，AE=3．求：(1)∠D的度数；(2)AF的长．6．探索题例8如图，四边形ABCD是平行四边形，∠BCD的平分线CF交边AB于点F，∠ADC的平分线DG交边AB于点G，且DG与CF交于点E．请你在已知条件的基础上再添加一个条件，使得△EFG为等腰直角三角形，并说明理由．二、添作中位线，妙证几何题三角形中位线定理：三角形的中位线平行于第三边，并且等于它的一半．这是三角形的一条很重要的性质，它包含了位置与数量两种关系．在题中，若有线段的中点，可过中点作第三边的平行线或取另一边中点构造中位线，运用中位线定理，实现线段或角的转移，从而迅速找到解题突破口，往往会使得某些看似无法解决的几何题化难为易，迎刃而解．例9如图，在△ABC中，ABAC，点D在AC上，且有CD=AB，E、F分别是AD和BC的中点，连结EF并延长与BA的延长线相交于点G，求证：AE=AG．例10如图，在四边形ABCD中，AC、BD相交于点O，且AC=BD，E、F分别是AD、BC的中点，EF分别交AC、BD于M、N．求证：∠OMN=∠ONM.例11如图，△ABC中，AD是BC边上的中线，E是AD的中点，BE的延长线交AC于点