“认识射线、直线和角”是苏教版《数学》四年级上册的教学内容。其教学目标是:使学生通过自学、观察、操作和交流,认识射线、直线的特征,了解线段、射线、直线之间的联系和区别;认识两点间的距离,知道两点间所有连线中线段最短。让学生通过比比划划辅助活动,借助想象建立“无限长”的概念。使学生积极参与学习活动,培养学生认真观察、积极思考、规范操作的良好习惯;感受图形与现实世界的密切关系,产生对数学的亲切感。在教学中,沈老 “Know the rays, lines and corners ” is the teaching content of the fourth grade of the Sujiao version of “Mathematics”. Its teaching objective is to enable students to understand the characteristics of rays and straight lines through self-study, observation, operation and exchange, to understand the connections and differences between line segments, rays and straight lines; to know the distance between two points and to know all the connections between two points The shortest line segment. Allow students to plan than through auxiliary activities, with the help of imagination to establish “infinite ” concept. Students actively participate in learning activities, training students to carefully observe, think positive, regulate the good habits of operation; feel the close relationship between graphics and the real world, resulting in a sense of intimacy of mathematics. In teaching, Shen old