conics question from SBHS trial '86 (2 Viewers)

[jkwii]

got a question, never seen it b4.

P and Q are the end points of a focal chord of the ellipse x^2/a^2 + y^2/b^2 = 1.
if P and Q have parameters alpha and beta, show that e^-1 = (sin alpha - sin beta)/sin (alpha - beta).????

help pls.....

 

[undalay]

here ya go.
sorry about the file quality, forum is max 100 kb per pic