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1、图形的相似2（Graphicsimilarity2）Avegetariandietisnotmuddygas;Godisnottosleepaloneintheheartdoesnotsitturbidity;turbidity;turbidityinreading.-ZengGuofanTopic:27.1graphicsimilarity(secondhours)teachlearnordermarkKnowledgeskill1.graspthedefinitionandrepresentationofsimilarpolygonsanddeterminewhetherth
2、etwopolygonsaresimilarbydefinition2.canbecalculatedaccordingtosimilituderatioMathematicalthinkingByanalogywiththeconceptofsimilarpolygons,weobtainthedefinitionofsimilartriangles,andunderstandtherelationshipbetweenspecialandgeneralSolvetheproblem1.canjudgewhetherthetwopolygonsaresimilarbydefin
3、ition,andtrainstudents'judgmentability2.,accordingtothesimilarityratiooflengthandangle,todevelopstudents'abilitytouseEmotionalattitudeByanalogywiththeconceptofsimilarpolygon,theteachingideaofpenetratinganalogyisgrasped,andtherelationbetweenspecialandgeneralisunderstoodAkeyThedefinitionandappl
4、icationofsimilartrianglesdifficultyDefinethelengthorangleofalinebydefinitionTopic:27.1graphicsimilarity(secondhours)AmatchthreeexercisesActivitytwointroducesthedefinitionandnotationofnewknowledgeactivityfoursimilartrianglesProblemsandsituationsTeacherstudentbehaviorDesignintentionPreparationa
5、ctivities:previewhomeworkReadingcomprehension:forfourlinesa,B,C,D,andifthetwolineratio(i.e.theirlengthratio)andtheothertwolinesofthesameratio,suchas(ab=cd),wesaythatthefourlinesisproportionaltotheline,referredtoasproportionalsegments.AmatchConceptsrelatedtosimilarpolygonsActivitytwointroducen
6、ewknowledgeExample.Figure,QuadABCDandEFGHissimilartothatfor1/2degreeangle,andthelengthoftheEF.Solution:quadrilateralABCDandEFGHaresimilar,andtheircorrespondinganglesareequal.L/1=/C=83,AngleA=angleE=118degreesInquadrilateralABCD,Angle2=360degrees(78degrees+83degrees+118degrees=118)Quadrilatera
7、lABCDandEFGHaresimilar,andtheircorrespondingsidesareproportional.Therefrom:Namely,Thesolutionisx=28(CM)ActivitythreeconsolidationexercisesFigure,thereisatriangularshapeofthelawn,thesidelengthis20m,inthelawnofthedrawings,thelengthof5cm,theothe
