圆环面积是在圆的面积计算基础上进行教学的,圆的面积计算学生接受起来并不太困难,但圆环却要把握住外圆和内圆这个形成圆环的本质问题,这个内容看似简单其实并不简单,如果在对圆环理解不够深刻的情况下,学生往往很容易出错,并且对于变式问题不能应对自如。 The circle area is calculated on the basis of the area of ​​the circle. It is not difficult for students to accept the calculation of the area of ​​the circle. However, the circle has to grasp the essence of the circle formed by the circle and the circle. It seems simple is actually not simple, if the understanding of the ring is not deep enough circumstances, students are often prone to error, and can not cope with the issue of variant.