圆是轴对称图形,又是中心对称图形.圆的对称性表明:解答与圆相关的点、线段、角的问题时,要有分类讨论的意识,做到考虑问题周全,分类不重不漏.1.两条平行弦之间的距离对于圆的一条弦(直径除外),总能找到与它关于圆心对称的另一条弦,这样的两条弦是平行相等的.所以两条平行弦有可能在圆心的异侧,还有可能在圆心的同侧. The circle is an axisymmetric figure, which is also a centrosymmetric figure. The symmetry of the circle shows that when it comes to answering the questions about points, line segments and corners related to the circle, it is necessary to have the consciousness of category discussion, .1. Distance between two parallel chords For a single chord of a circle other than a diameter, one can always find another chord that is symmetrical about its center, so that the two chords are parallel and equal. It may be on the opposite side of the center of the circle, and possibly on the same side of the center of the circle.