七年级下册图形的全等备课讲稿.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,10.5,图形的全等,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,【,教学目标,】,1.,知道全等图形、全等多边形、全等三角形的概念及性质；能找出全等多边形、全等三角形的对应元素，会利用图形的全等解决一些简单的问题；,2.,培养学生观察、探索、分析、归纳等能力；,3.,在学生观察的过程中，激发学生学习几何的积极性及主动探索、敢于实践的科学精神。,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,全等多边形的性质与识别方法,【,教学重点,】,【,教学难点,】,平移、旋转、翻折等基本运动对全等图形的影响,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,回忆：,1,、我们学过哪三种基本变换（也叫做运动）？,轴对称（翻折）、平移、旋转,2,、以上三种基本变换有哪些,共同,的特征：,图形的形状、大小不变，位置改变。,对应线段相等。,对应角相等。,3,、如何判断两个图形的形状和大小是否完全相同？,可以通过,轴对称、平移和旋转,等变换，把两个图形叠合在一起，观察它们是否完全重合。,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 20042011 Aspose Pty Ltd.,能够,完全,重合的两个图形叫做,全等图形,。,找一找,：,从图中找出形状和大小完全一样的图形,（,1,）,（,2,）,（,3,）,（,4,）,（,5,）,（,6,）,（,7,）,（,8,）,（,9,）,（,10,）,（,11,）,（,12,）,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,从图中找出形状和大小完全一样的图形,（,1,）,（,2,）,（,3,）,（,4,5,）,（,6,）,（,7,）,（,8,）,（,9,）,（,10,）,（,11,）,（,12,）,5,和,11,是由,_,变换得到的全等图形。,10,和,7,是由,_,变换得到的全等图形。,9,和,4,是由,_,变换得到的全等图形。,平移,平移,旋转、平移,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,两个经过,平移、旋转、翻折,等运动能够,完全重合,的图形称为,全等图形,。,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,找出图中的全等图形,（,1,）,（,2,）,（,3,）,（,4,）,（,5,）,【跟踪练习一】,（,6,）,（,7,）,（,8,）,（,9,）,（,10,）,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,（,1,）多边形经过,变换而完全重合，称为,全等多边形。,（,2,）两个全等多边形，经过变换而重合，相互重合的顶点叫做,，相互重合的边叫做,，相互重合的角叫做,。,翻折、平移和旋转,对应顶点,对应边,对应角,A B,C D,B,D,A C,A,B E,C D,A,E B,D C,【知识点二】,全等多边形,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,D,E,F,A,B,C,能够,完全重合,的两个三角形叫做,全等三角形,。,全等三角形的定义及表示方法,【知识点三】,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,D,E,F,A,B,C,如上图：,ABC,与,DEF,全等,记作：,ABCDEF,“,全等,”符号：“,”,读作：,ABC,全等于,DEF,全等的表示方法,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,A,C,B,F,E,D,想一想,能否记作,ABC DEF,?,应该记作：,ABC DFE,原因,:,A,与,D,、,B,与,F,、,C,与,E,对应,。,通常把对应的顶点字母写在对应位置上,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,N,M,S,O,T,D,C,O,A,B,仔细观察,再用,全等符号,表示下列两组全等三角形,.,AOB,DOCOAB,ODC,MON,SOT,【跟踪练习三】,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,A,B,C,全等三角形的对应边相等，对应角相等。,ABCDEFAB=DE,、,BC=EF,、,CA=FD A=D,、,B=E,、,C=F,D,E,F,全等三角形的性质,【知识点四】,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,（,1,）已知,AMC,BMD,请找出所有对应顶点、对应边和对应角。,（,2,）仅从,AMC,BMD,能正确找出,所有,的对应元素吗？,在图上又是怎样找对应元素的呢？,【跟踪练习四】,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,A,B,C,D,有公共边的，公共边是对应边,.,【方法,总结】,1.,在图上找全等三角形的,对应边,A,B,C,D,E,F,一对最长的边是对应边，一对最短的边,是对应边,.,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,C,D,A,B,E,B,D,A,C,有公共角的，公共角是对应角,.,有对顶角的，对顶角是对应角,.,最大角与最大角（最小角与最小角）,为对应角。,【总结】,2.,在图上找全等三角形的,对应角,O,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,【总结】,3.,在表达形式上找对应边和对应角,利用字母的对应位置来确定对应边和对应角。,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,C,D,A,B,E,1,、如下图,ADC,AEB,则,EB=_,AE=_,BD=_,CDA=_.,【,巩固练习,】,CE,AD,DC,BEA,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,1,A,E,B,C,D,50,95,2,、如图，已知,ABDACE,，且,1=45,ADB=95,则,AEC=,C=,.,3,、如图，如果,ADE,CBF，那么AE,CF吗？,_(,口答,“,是,”,或,“,不是,”,),是,A,C,D,B,E,F,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,3,、若,MNP,NMQ,且,MN=8,NP=7,PM=6,则,MQ,的长为,_.,1,A,E,B,C,D,4,、如上右图，已知,ABCDFE,，且,AC,与,DE,是对应边，若,BE=14CM,，,FC=4CM,，则,BC=.,A,B,C,F,E,D,50,95,9CM,7,2,、如上左图，已知,ABDACE,，且,1=45,ADB=95,则,AEC=,C=,.,2,、如上左图，已知,ABDACE,，且,1=45,ADB=95,则,AEC=,C=,.,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,4,、已知,ABCDEF,，,ABC,的周长是,40cm,，,AB=10cm,，,BC=16cm,，求,DF,的长度。,解：,ABCDEF,（已知）,AC=DF,(,全等三角形的对应边相等）,ABBCAC,40,（,cm,）,（已知）,AC=40-10-16=14,（,cm,），,DF=14cm,A,B,C,D,E,F,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,5,、如图，已知,ABC,沿,BC,翻折后，得到,DBC,。,ABC,和,DBC,有什么关系？,若,ACD=110,，,A=100,，求,ABC,的度数？,解：,ABCDBC,ABCDBC,ACB=,DCB,又,ACD=110,ACB=,DCB,=55,在,ABC,中，,A,ACB,ABC180,，,A=100,，,ACB=55,ABC=25,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,6.,如图,:ABCAEC,B=30,ACB=85,求出,AEC,各内角的度数,.,A,B,C,E,解：,AECABC,E=B=30,ACE=,ACB,=85,EAC=BAC=180,-30,-85,=65,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,7.,如图,ABCDEF,求证,:AD=BE,B,A,E,F,C,D,ABCDEF,AB=DE,AB-BD=DE-BD,即,AD=BE,证明：,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,如图,ABCEBD,问,1,与,2,相等吗,?,若相等请证明,若不相等说出为什么,?,B,A,E,2,1,F,C,D,O,解：,EBD,ABC,A=E,在,AOF,与,EOB,中，,AOF=EOB,根据三角形内角和为,180,1=2,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,通过这节课的学习，你对,全等图形有哪些认识？,1.,全等图形、全等多边形、全等三角形,3.全等多边形的性质,4.全等三角形的性质,2.对应顶点,、对应边、对应角,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,