Some examples are given by inscribed and circumscribed circles ofpolygons, lines intersecting and tangent toconic sections, thePappusandMenelausconfigurations of points and lines.

• 一些例子所给予者和限制各界的多边形，线相交和相切的圆锥部分，帕普斯和墨涅拉俄斯配置的点和线。