内容正文:
9.1 三角形的边
说一说:
关于三角形,你都知道些什么?
自主学习课本第100-101页 观察与思考、大家谈谈的
内容,继续了解:
1、三角形的概念
2、三角形的边、顶点、内角
3、三角形的表示方法
4、三角形的两种分类方法
5、三角形三边之间的关系及应用
1、三角形的定义 由不在同一条直线上的三条线段首尾顺次连结所组成的图形,叫做三角形。
所以,三角形的特征有:
(1)不在同一直线上(2)三条线段
(3)首尾顺次连接(形成封闭图形)
什么是三角形?
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2、三角形的表示:
A
B
C
三角形用符号“△”表示
记作“△ ABC”读作“三角形ABC”
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