A projectile is fired in such a way that its horizontal range is equal to three times its maximum height. What is the angle of projection from the horizontal?
v^2/g sin^2θ = 3v^2/2g sin^2θ
sin^2θ = 3/2 sin2θ
sin^4θ = 9 sin^2θ cos^2θ
sin^2θ = 9 cos^2θ
tan^2θ = 9
tanθ = ±√3
θ = 60°