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离心率是描述圆锥曲线的重要的几何量,它既与圆锥曲线的基本参数a,b,c密切相关,又与圆锥曲线的形状联系紧密,求圆锥曲线的离心率或研究取值范围的问题一直是高考考查的热点.求圆锥曲线的离心率常有以下三种解法.一、定义法由圆锥曲线的定义e=c/a可知,只需求得a、c或a与c之间的关系即可.例1若双曲线x~2/a~2-y~2/3=1(a>0)的离心率为2,则a等于().
Centrifugal rate is an important geometric quantity describing the conic. It is closely related to the basic parameters a, b and c of the conic, but also to the shape of the conic. The eccentricity of the conic or the range of the research value Has always been a hot spot for college entrance examination examining the coning curve of the centrifugal rate often have the following three solutions.First, the definition of law by the definition of conic curve e = c / a shows that only need to get a, c or a and c relationship Example 1 If the eccentricity of the hyperbola x ~ 2 / a ~ 2-y ~ 2/3 = 1 (a> 0) is 2, then a equals ().