离心率是圆锥曲线的一个重要性质,是描述曲线“扁平程度”或“张口大小”的一个重要参量,在解析几何中显得极为重要,它常与“定义”、“焦点三角形”等联系在一起,因此有关求解离心率的取值范围的问题,综合性强、难度大、涉及的知识面广,求解方法灵活多变.一、正余弦定理和均值不等式求解 Centrifugal rate is an important property of the conic curve and is an important parameter to describe the curve “flatness ” or “mouth size ”. It is extremely important in analytic geometry. It is often associated with “definition ”, “ Focal triangle ”and so on, so the problem of solving the range of centrifugal rate, comprehensive, difficult, involving a wide range of knowledge, the solution is flexible. First, the cosine and cosine inequality inequality solution