一、谈话导入师:同学们,今天我们来认识圆,请看大屏幕,仔细观察,圆和我们以前学过的图形有什么不同?(出示课件)生:以前学过的图形有角,圆没角。师追问:圆为什么没角?生:因为圆是曲线图形。(板书:曲线)师:课前,同学们都预习了教材,下面请同学们以小组为单位汇报预习情况。 First, the conversation imported teacher: Students, today we come to know the circle, see the big screen, carefully observe the circle and what we have learned before the graphics What is the difference? (Show courseware) Students: previously learned graphics Angular, round No corner. Teacher asked: Why is the corner angle? Health: Because the circle is a curve. (Form Book: Curves) Teacher: Before class, the classmates previewed the teaching materials. Next, I would like to ask the students to report the preview situation as a group.