Quote by hotvette
What you need to do is find the time it takes for the range (x) to be R/2 and then find θ such that the height (y) is H.
Your expression is valid for a triangle connecting the starting point to the peak but that doesn't have anything to do with the projectile problem.

I found the position function in the x direction and set it equal to R/2. This gave me that the time, t, such that the position of x is R/2 is t=v
_{0}sin(2θ)/2gcosθ.
I can use trig identities to simplify this to t=v
_{0}sinθ/g
I can find the position function of y: S
_{y}=v
_{0}t4.9t
^{2}, but I'm not sure what to plug in.
I'm also very confused as to how I'm supposed to express the answer in terms of H and R, as the question specifically asks.