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例题设椭圆x~2/a~2+y~2/b~2=1(a>b>0)的左,右焦点分别为F_1,F_2,若椭圆上存在点P,使∠F_1PF_2=90°,则离心率e的取值范围是.解解法一:利用曲线范围求解
Example Let the left and right focal points of the ellipse x2 / a2 + y2 / b2 = 1 (a> b> 0) be F_1 and F_2, respectively. If there exists a point P on the ellipse, let ∠F_1PF_2 = 90 °, then the value of the centrifugal rate e range is. Solution one: the use of curve range solution