Simple dude.
use S = ut + at^2/2

so the 2 eqns will be
s = 1/2*g t^2 /4
and
s/ cos@ = 1/2 * gcos@ t^2

dividing the 2 equations

cos@ = 1/4cos@
cos^2 @ = 1/4
cos@ = 1/2
@ = 60 degrees ( with the vertical)