Question

已知椭圆X^2/a^2+y^2/b^2=1(a＞b＞0)的三个顶点B1(0,-b)B2(0,b),A(a,0),焦点F(

Answer 1

kB1F = b/c; kAB2 = -b/a

B1F⊥AB2 所以

kB1F*kAB2 = -1 因此

b^2 = ac = a^2-c^2

所以 e^2+e-1 = 0 e=(√5-1)/2