[Solution from source] At the top the projectile is at height H and horizontal distance R/2. tan α = H/(R/2) = (u² sin²θ/2g)/(u² sinθ cosθ/g) = tanθ/2 = 1/2 for θ = 45°. So α = tan⁻¹(1/2); 45° would be the launch angle, not the elevation of the highest point. Answer (4).