Given that the chord length perpendicular to the focus of the ellipse is √ 2, how to get (2B ^ 2) / a = √ 2

Given that the chord length perpendicular to the focus of the ellipse is √ 2, how to get (2B ^ 2) / a = √ 2

The question is not comprehensive, it should be: perpendicular to the major axis of the ellipse and beyond the focus of the ellipse If so, then this string is called the sine focus string, and the derivation process is as follows: let the elliptic equation x ^ 2 / A ^ 2 + y ^ 2 / b ^ 2 = 1, half of the orthogonal string be l, and there is an intersection (C, l), l > o between the over focus F2 and the ellipse, and the coordinate value of this intersection satisfies the elliptic equation C ^ 2 / A ^ 2 + L ^ 2 / b ^ 2 = 1, so we can get l = B ^ 2 / a (Note: A ^ 2-C ^ 2 = B ^ 2), and the length of the sine focus string is 2L = 2B ^ 2 / A. in this problem, it is equal to 2 ^ (1 / 2)