A ball is thrown from the ground to a wall 3 m high  at a distance of 6 m . If the ball just clears the wall and falls 18 m away from the wall, the angle of projection of ball is

Here,   R=u2sin2θg=24∵  y=xtanθ-gx22u2cos2θ         3=6tanθ-36g2u2cos2θ                         …(ii)From Eq. (i), we get             gu2=sin2θ24=sinθcosθ12Substituting in Eq. (ii), we get        3=6tanθ-32tanθ=92tanθ⇒θ=tan-123