as far as i know the range of an obliquely projected body which is projected with a velocity of u with some angle $\theta$ with the horizontal under the action of gravity is
R=$u^2sin2\theta$/g by which we can calculate the range of projected body when it comes to the same level of the point of projection
but how to calculate the remaining distance which it covered below the point of projection
i got this formula on the web but i cant prove this
Can any one help me by suggesting me what concept I am missing to calculate the range?