一些材料在讲圆面积公式时,为使学生更深刻地了解圆面积公式的意义,进一步验证公式,说明圆面积就是半径平方这样的正方形三倍多一些,采取了一些方法。例如,作一个圆外切正方形,再把它划分为许多等分的小方格,用数方格的方法,把圆面积与它的外切正方形面积进行比较。还有些教师,把圆外切正方形划分成以半径为一边的四个等分正方形,说明圆面积不足四个半径平方这样的正方形面积,只有三个多一些。还有些材料,将圆面积与它拼凑的长方形面积 Some materials in the circular area formula, in order to enable students to better understand the meaning of circular area formula, to further verify the formula, indicating that the square area is the radius of the square more than three times, to take some methods. For example, to make a circle circumscribing a square, divide it into many smaller squares, and use a square method to compare the circle's area with its circumscribed square area. Still other teachers divide the square of a circumscribed circle into four equally-divided squares of one radius, indicating that there are only more than three square areas of a circle with a radius of less than four radii. There are also some materials that will circle the area with its rectangular patchwork