Question

Can somebody explain it to me please?​

Answer 1

Answer:

45°.

It is a property of the parabolas.. When the angle between a parabola and the x-axis is 45° the range is maximum.

Answer 2

Range be R and height be h

$\boxed{\sf R=\dfrac{u^2sin2\theta}{g}}$

$\boxed{\sf h=\dfrac{u^2sin^2\theta}{2g}}$

u=initial velocity

theta is angle of projection.

g=acceleration due to gravity

ATQ

$\\ \sf\longmapsto R=2h$

$\\ \sf\longmapsto \dfrac{u^2sin2\theta}{g}=\dfrac{2u^2sin^2\theta}{2g}$

Cancelling required ones

$\\ \sf\longmapsto sin^2\theta=sin2\theta$

sin2O=2sinOcosO

$\\ \sf\longmapsto sin^2\theta=2sin\theta cos\theta$

$\\ \sf\longmapsto \dfrac{sin^2\theta}{sin\theta cos\theta=2$

$\\ \sf\longmapsto \dfrac{sin\theta}{cos\theta}=2$

$\\ \sf\longmapsto tan\theta=2$

$\\ \sf\longmapsto \theta=tan^{-1}(2)$

$\\ \sf\longmapsto \theta=63.4°$

Done

Option B is correct