At what angle to the horizon was the stone thrown with an initial speed of 20 m / s

At what angle to the horizon was the stone thrown with an initial speed of 20 m / s if it fell after 3 s at a distance of 30 m from the place of throwing?

We are looking for a by the formula S = v0cosα * t. It is known that S = 30m, v0 = 20m / s. v0cosα is the projection of the velocity along the x-axis. Find the cosine cosα = S / (v0 * t) = 30 / (20 * 3) = 0.5. With a cosine value of 0.5 -> α = 60
Answer: 60 degrees