[相似三角形复习——比例式、等积式的几种常见证明方法.ppt

1.通过本节课的学习，你有什么收获？还有什么困惑吗？ 2.你对自己本节课的表现满意吗？为什么？ * 2 0 0 6. 0 4 .2 0. 相似三角形复习（2） ——比例式、等积式的几种常见证明方法 龙台镇中 吴刚先 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 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:如图, ∠ACB=90°,AD=DB,DE⊥AB于D交AC于E,交BC的延长线于F,试说明: DC2=DE·DF 利用相似三角形的性质 A D B F C E Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 2. 如图,在直角梯形ABCD中,AB∥CD, AB⊥BC,对角线AC⊥BD,垂足为E,AD=BD,过点E作EF∥AB交AD于F, 试说明 （1）AF=BE （2） AF2=AE·EC 利用等线段代换 D C A B F E Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 3.已知,如图,在△ABC中, ∠BAC=90°, AD⊥BC,垂足为D,E是AC的中点,ED的延长线交AB的延长线于点F. 试说明:AB：AC=DF：AF 利用等比式代换 A C B D F E 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,如图,CE是直角△ABC的斜边AB上的高,在EC的延长线上任取一点P,连接AP,作BG⊥AP,垂足为G,交CE于D, 试说明:CE2=ED·EP. 利用等积式代换 P G A B E C D Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. D C A B F E A C B D F E P G A B E C D BE2=EA·EC AC:AB=AD:BD EC2=EA·EB Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. C A B D 在这一个图形中,有两个垂直,有____对相似,有___对互余的角,有_____组对应成比例的线段,它们分别是 三 四 五 AC2=AD·AB BC2=BD·AB CD2=AD·BD AC:AD=BC:CD BC:BD=AC:CD Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. A B D E C 如上图, ∠BAC=120°