Well, you can put the quantity under the square root under common denominator v0 so that you will cancel the v0 at the outside and will get [v02-2gtv0sinx+(gt)2]1/2
For a projectile launched with velocity at angle , what is the magnitude of the velocity vector at time ?
Apply the pythagorean theorem and you'll end up where I am.
Unless I did something wrong. Stayed up till 2 AM doing this stuff.