quadrature of a circle

例句：

1. 1. The circle's circumference is 2πr.
   这个圆的周长是2πr。
2. 2.The quadrant of the circle isdivided into four equal parts by the radius.
   圆的四分之一被半径分成四个相等的部分。
3. 3. The quarter-turn rule states thata line drawn through the center of acircle will intersect it at two points.
   四分之一转规则表明，通过圆心画一条线，它将与圆相交于两点。