我们知道,圆是以其圆心为中心的中心对称图形,经过圆心的每一条直线都是它的对称轴.圆上任意两点间的线段叫做弦,经过圆心的弦叫做圆的直径,同一个圆的所有直径都相等,直径所对的圆周角都是直角,在直角坐标系中,对于圆我们有如下熟知的性质:已知AB是圆x2+y2=r2(r>0)的任一直径,点 We know that a circle is a center symmetric graph centered on its center and every line passing through the center of a circle is its axis of symmetry.The line between any two points on a circle is called a string and the string passing through the center is called a circle of the same diameter All of the circles have the same diameter, and the diameters of the circles have a right angle. In Cartesian coordinates, we have the following well-known properties for a circle: AB is known to be any of the circles x2 + y2 = r2 (r> 0) Diameter, point