[课前思考]“圆的面积”是人教版小学数学教材六年级上册第五单元的教学内容,也是一节让教师纠结、学生困惑的疑难课例。首先,圆面积公式的推导,学生无法沿用割补(如平行四边形)、拼合(如三角形、梯形)等已有策略,找不到尝试的路径;其次,教材中将圆先等分再拼组,与学生的已有经验,如圆周长的探索经历、割圆术的方法渗透衔接不够,所谓的探究只是机械地模仿;特别是因为学生手中的圆纸片大小终归是有限的,等分 [Thinking before class] “Circle area ” is the teaching content of the fifth unit of the sixth grade of the mathematics textbooks for the PEP, and also a difficult lesson for teachers to tangle and confuse students. First, the deduction of circular area formula, students can not follow the existing strategy of cutting (such as parallelogram) and flattening (such as triangle and trapezoid), and can not find the path to try. Second, , With the existing experience of students, such as the circumference of the exploration experience, the method of circumcision penetration is not enough, the so-called inquiry is only a mechanical imitation; especially because students in the hands of the round paper size is always limited,