A circle is a geometric figure. When a line segment rotates around one endpoint on a plane, the trajectory of the other endpoint is called a circle. By definition, compasses are usually used to draw circles.

Pi, generally expressed by π, is a common mathematical constant in mathematics and physics. It is defined as the ratio of the circumference to the diameter of a circle. It is also equal to the ratio of the area of a circle to the square of its radius. Accurate calculation of geometric shapes such as circle perimeter, circle area and sphere volume is the key value. In the analysis, π can be strictly defined as the smallest positive real number x satisfying sin(x)=0.

Zu Chongzhi (429-500) was an outstanding mathematician and scientist in China. People in the Southern and Northern Dynasties, Han people, the word Wen Yuan. Born in Yuanjia for six years, he died in Hou Yongyuan and Qi Hun for two years. My ancestral home is in Qixian County, Fanyang County. In order to escape the war, Zu Chongzhi's grandfather, Zuchang, moved from Hebei to Jiangnan.

Zuchang was once a "great craftsman" in Liu Song, in charge of civil engineering; Zu Chongzhi's father is also a DPRK official. Zu Chongzhi received scientific knowledge from his family since childhood. When I was young, I entered Hualin University and engaged in academic activities. Throughout his life, he served as an official in South Xuzhou (now Zhenjiang), such as Shi, Fu joined the army, Lou Junling (now northeast of Kunshan), Servant Shooter and Changshui Captain.

Extended data:

1. The locus of a point whose distance from a fixed point is equal to a fixed length is a circle with the fixed point as the center and the fixed length as the radius;

2. The locus of the point with the same distance at both ends of the line segment is: the middle vertical line of the line segment;

3. The trajectory to the point with the same distance on both sides of the angle is: the bisector of the angle;

4. The locus of points with equal distance to a straight line is: two points are parallel to this straight line, and the distance to this straight line is equal to a fixed length.

5. The locus of a point with equal distance to two parallel lines is: the positional relationship between a straight line point parallel to the two parallel lines and a circle with equal distance to the two straight lines: the point is in the circle. The positional relationship between a straight line and a circle: there is no intersection between a straight line and a circle. A straight line and a circle have an intersection. A straight line and a circle have two intersections. The positional relationship between circles: the circumscribed circle has an intersection point, two intersections, and an intersection point d=R-r, excluding intersection point D.