

When projectile is thrown from ground, then-
Range R= u2 sin2θ/g
Height H = u2 sin2θ/2g
When Range is equal to Height,
R=H
u2 sin2θ/g = u2 sin2θ/2g
sin2θ = sin2θ/2
2 sinθcosθ = sin2θ/2
4 cosθ = sinθ
4 = tanθ
So angle θ= tan-1(4) for which R= H
= 75.96º
