笔者听了北京吴正宪老师的一节数学课“圆的周长”,教者通过质疑问难,启发学生思维,引导学生发现规律。其中一个片断颇为精彩,现摘录如下: The author listened to a section of mathematics lesson entitled “Circumference of Circles” by a Beijing teacher Wu Zhengxian. By asking questions and questions, the instructors inspired the students' thinking and guided the students to discover the law. One of the pieces is quite exciting and is excerpted below: