苏教版四年级上册数学《角的认识》公开课课件PPT.ppt

绿色圃中小学教育网 直线射线和角的认识 * * 引 入 新 授 练习 巩固练习 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 线段是直的， 它有两个端点， 长度是有限的。 复习线段概念 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 这些灯射出的光线 都可以看作射线 引入射线教学1 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. c 认识射线 引入射线教学2 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 把线段的一端无限延长，就得到一条射线。 射线的概念 ● ● ● Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 射线也是直的线，它有 一个端点，是无限长的。 射线的概念 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 把线段的两端都无限延长，就得到一条直线。 直线的引入 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 直线没有端点， 是无限长的。 直线的特征 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 射线、直线和线段 相比，有什么相同？ 有什么不同？ 线段，射线，直线的异同点 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 线段 射线 直线 不 同 点 两个端点 一个端点 没有端点 有限长 无限长 无限长 线段，射线，直线的异同点 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 下面哪些是线段，哪些 是射线，哪些是直线？ 线段，射线，直线巩固练习 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 两点确定一条直线 线段，射线，直线巩固练习 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 生活中常常应用两点 确定一条直线的知识。 你还能找到这样的例子吗？ 线段，射线，直线巩固练习 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. A B 想一想 连结A、B两点的三条线，哪一条最短？ 连结两点的线段的长度叫做这两点间的距离。 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspo