Question

A body is projected at such an angel that the horizontal range is three times the greatest hight . the angle of projection is ...

Answer 1

we know , 

  horizontal range = u²sin2Ф/g

  maximum height = u²sin²Ф/2g

A/C to question,

    horizontal range = 3× maximum height 

    u²sin2Ф/g  =  3 × u² sin²Ф/2g 

   { sin2Ф = 2sinФ.cosФ }

    2sinФ.cosФ  = 3/2. sin²Ф

    tanФ = 4/3 

Ф = tan⁻¹(4/3)