There is only horizontal component of velocity at the highest point because at highest point vertical component of velocity is zero, body begins to come downwards from the highest point. ∴ucosθ=2ucosθ =21=cos60∘ ⇒θ=60∘
ange R=g2u2sinθcosθ R=g2u2×sin60∘cos60∘ R=2g3u2