\(\Rightarrow u=20 \mathrm{m} / \mathrm{s}\)
\(t=\frac{2 u \sin \theta}{g}\)
and \(R=(u \cos \theta+20)\left(\frac{2 u \sin \theta}{g}\right)\)
Put \(\frac{d R}{d \theta}=0\)
\(\Rightarrow \cos \theta=1 / 2\)
\(\Rightarrow \theta=60^{\circ}\)
આપેલ : $1\, {ly}=9.46 \times 10^{15} \,{m},$ $\, {AU}=1.5 \times 10^{11}\, {m}$