A projectile can have same range from two angles of projection with same initial speed. If h1 and h2 be the maximum heights, then
R=h1h2
R=2h1h2
R=4h1h2
R=u2sinθg at angles θ and 90°-θ
Now, h1=u2sin2θ2g and h2=u2sin290°-θ2g=u2cos2θ2g
h1h2=u2sin2θg2·116=R216
∴ R=4h1h2