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求离心率(范围)是圆锥曲线里常考的一类问题.主要有三种方法:1不等式法(即将题设条件转化为关于变量的不等式,再解不等式或用不等式的性质推出结果);2函数法(即将变量范围转化为某个函数的值域);3几何法(即利用几何性质,通过数形结合求解).其中难点是获取关于e(或c/a)的等量或不等关系或函数关系,常常需要利用圆锥曲线的性质(焦半径范围、图像上的点横纵坐标范围、三角形三边关系、正弦定理、余弦定理、均值定理等)
The eccentricity rate (range) is often a type of problem in the conic. There are three main methods: 1 inequality (ie, transforming the problem set into inequalities about variables, then solving inequalities or using inequalities); 2 The function method (ie, transforming the range of a variable into the range of a function); 3 The geometric method (ie, using geometric properties, solved by a combination of number and form). The difficulty is to get an equal or unequal amount of e (or c / a) Relationships or functional relationships often require the use of the properties of the conic (focal radius range, horizontal and vertical coordinate ranges of the image, triangular trilateral relations, sine, cosine, mean, etc.)