A Circumconic passes through a triangle's vertices; an Inconic is tangent to the sidelines. We study the variable geometry of certain conics derived from the 1d family of 3-periodics in the Elliptic Billiard. Some display intriguing invariances such as aspect ratio and pairwise ratio of focal lengths.

中文翻译：

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椭圆台球中 3 周期的圆周不变量和非圆锥不变量

Circumconic 通过三角形的顶点；Inconic 与边线相切。我们研究了从椭圆台球中 3 周期的 1d 族导出的某些圆锥曲线的可变几何形状。一些显示有趣的不变性，例如焦距的纵横比和成对比率。