Find the distribution of R = A sin , where is a fixed constant and is uniformly

Find the distribution of R = A sin θ, where is a fixed constant and is uniformly distributed on (- π/2, π/2). Such a random variable R arises in the theory of ballistics. If a projectile is fired from the origin at an angle from the earth with a speed v, then the point R at which it returns to the earth can be expressed as R = (v²/g) sin2α, where is the gravitational constant, equal to 980 centimeters per second squared.