圆锥曲线有许多丰富、有趣的性质 ,是高中各类考试考查的重点内容 ,本文对其中的几个定值问题加以总结 .1　焦点弦性质圆锥曲线过焦点的弦被焦点分成长为ｍ ,ｎ的两部分 ,则 1ｍ +1ｎ =2ｅｐ.证明　由圆锥曲线统一的极坐标方程ρ= ｅｐ1 -ｅｃｏｓθ.可设ｍ =ｅｐ1 -ｅｃｏｓθ Conic curves have many rich and interesting properties, and they are the focus of examinations in high school exams. This article summarizes several of the fixed questions. 1 Focus chord properties Conical curves over the focus of the chord are developed into m,n For the two parts, then 1m +1n = 2ep. Prove that the polar equation is unified by the conic section ρ = ep1 -ecosθ. Let m = ep1 - ecosθ