I came across a problem in my book with this diagram,
A machine gun is mounted on the top of a tower 100 m high. At what angle should the gun be inclined to cover a maximum range of firing on the ground below? The muzzle speed of bullet is 150 ms^-1 .
I read that when a body is projected with a certain angle from the ground it returns with the same angle and speed with which it was projected. But in this case the projectile goes below the level of projection. How does it still hit the ground at an angle $\theta$?