In this paper, a fixed value theorem for directed areas of a kind of triangles in elliptic circumscribed polygons is obtained, thus some results, including the famous Brianchon theorem for elliptic circumscribed triangles, are deduced easily.

• 本文给出椭圆外切 2n +1边形中一类切顶线三角形有向面积的一个定值定理及其若干推论 ,其中包括射影几何中著名的Brianchon定理在椭圆外切三角形中的情形