一、认识多边形请同学们观察图1中的几个图形.你能归纳出它们的共同特点吗?仔细观察后你会发现:这些图形都是由在同一平面内的多条线段顺次首尾相接而成的,其中任一线段都只与和它首尾相接的两条线段有公共点,任何相邻的两条线段都不在同一直线上.符合上述特点的图形就叫做多边形.构成多边形的各条线段叫做多边形的边;这些线段的端点叫 First, recognize the polygons Please observe the students in Figure 1 of several graphics Can you sum up their common characteristics? After careful observation you will find: These graphics are in the same plane by a number of line segments in sequence Then any of the line segments are only common to the two line segments connecting to it, and any two adjacent line segments are not on the same line. The figure meeting the above characteristics is called a polygon Each line segment is called the edge of the polygon; the end point of these lines is called