【教学内容】苏教版四年级上册第77~78页。【教学重点、难点】理解直线、射线和角的特征。建立“无限长”的概念。【教学过程】一、情境导入,激活经验1.回顾旧知。出示情境图:提问:从张宁家到学校有几条路线可以走?哪一条最近?(根据回答,课件动态演示 Teaching content】 【Soviet version of the fourth grade on the first 77 ~ 78 pages. [Teaching emphasis, difficult] Understand the characteristics of the line, ray and angle. Create the concept of infinite number. Teaching process First, the situation is imported, activate the experience 1. Review the old knowledge. Scenario shown: Question: From Zhang Ning to the school there are several routes to go? Which one recently? (According to the answer, courseware dynamic demonstration