This question is quite difficult. We mainly study the definition and properties of ellipse and hyperbola. Using cosine theorem and Cauchy inequality is the key to solve this problem. Cauchy inequality is a difficult point. See/Exercise/Mathematics /804450 for the answer. You just need to know how to use Cauchy inequality. I can basically do this problem. I won't ask you again. I hope you can adopt it. Thank you.

F 1, F2 is the common focus of ellipse and hyperbola, and p is the common point. And ∠F 1PF2=π/3, find the maximum value of the sum of the reciprocal of eccentricity of ellipse and hyperbola ().

1. 3/3 of the number of 4 elements

B, 2 root number 3/3

c、3

d、2

I hope you can adopt it. I wish you progress in your study. What?