[Tatsu]

Racsan, your calculations dont make sense

once the ball reaches maximum trajectory, drag DECREASES ay not increases it.. so the plus sign there doesnt make sense.. you need an if statement.. if vy is negative, then change the sign on drag.

Anyway my data say

.798 radians at 9.97 meters launched at 12 m/s

The only simplifying assumption I made was that
drag in x direction = dragcoef*vx^2 rather than taking the sine of the drag.. its accurate enough I believe.

Tatsu