[integral from 0 to pi/2] dx/SQRT(a - cosx)

(a >1)

I need to write this in terms of the elliptic integrals F

the elliptic integral of the first kind is F(k,q) = [integral from 0 to q]

$\displaystyle

du/SQRT(1 - (ksinu)^2)

$

PLEASE if you know anything about elliptic integrals I need your help!

I do not see a starting point on this!

I know elliptic integrals are tricky and ambiguous and all that...I merely need to REWRITE the given integral in terms of F

thank you in advance for your help!