刘徽指出：“割之弥细,所失弥少.割之又割,以至于不可割,则与圆周合体而无所失矣.”（《九章算术》方田章圆田术刘徽注）这就是说,圆内接正多边形的边数无限增加的时候,它的周长的极限是圆周长,它的面积的极限是圆面积.
In a circle,when an isogon unlimited number of margin increase,the limits of its perimeter is circumference,and its size limited is the area of the circle.