Well, you can put the quantity under the square root under common denominator v_{0} so that you will cancel the v_{0} at the outside and will get [v_{0}^{2}-2gtv_{0}sinx+(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.