A 2 = 2c 2, b 2 = c 2 can be obtained, and the elliptic equation is

x^2/2c^2+y^2/c^2= 1，

Substituting B coordinates can get the solutions of c = 2, a = 2 √ 2 and b = 2.

The elliptic equation is x 2/8+y 2/4 = 1,

2、A(a，0)，B(x 1，y 1)，C(-x 1，-y 1)。

k 1 k2 =[y 1/(x 1-a)][-y 1/(-x 1-a)]

=(y 1)^2/[(x 1)^2-a^2]

=(y 1)^2/[(x 1)^2-2c^2]

=(y 1)^2/[2(y 1)^2]

=- 1/2

(Next, use X 2/2C 2+Y 2/C 2, and change it to

X 2+2y 2 = 2c 2, that is, X 2-2c 2 = 2y 2)

3, the symbols behind are not fun,