OR: At what angle should a body be thrown so as to hit the most distant point?
Let a body be projected with velocity $u$ making an angle $\theta$ with horizontal. Then, the horizontal range $R$ is given by,
The range $R$ will be maximum when \[\sin2\theta=1\] \[\sin2\theta=\sin90°\] \[2\theta=90°\] \[\therefore\theta=45°\]
Hence, the angle of projection for maximum horizontal range is $45°.$
[Read: Projectile Motion]