本文介绍了圆锥曲线的焦点弦(或焦半径)与离心率的一条新关系式及其推论,并说明了其在解高考题中的应用.定理设点F是离心率为e,焦点在x轴上的圆锥曲线的一个焦点,P为焦点F到其对应准线的距离,r为该圆锥曲线的焦半径,则有:e=P±rrcosθ(*)成立其中:(1)若该圆锥曲线为椭圆,当定点 This paper introduces a new relationship between the focal chord (or focal radius) and the eccentricity of the conic curve and its inference, and explains its application in solving the college entrance examination question. The theorem, set point F is the eccentricity e, the focus is at x A focal point of the conic section on the axis, P is the distance from the focal point F to its corresponding quasi-line, and r is the focal radius of the conic section. Then: e = P rr rrcos θ (*) holds where: (1) if the cone The curve is elliptical when fixed