\(T=\frac{2 u \sin \theta}{g} \Rightarrow u=\frac{g T}{2 \sin \theta}\)

\(R=\frac{2 u^2 \sin \theta \cos \theta}{g}\)

\(R=\frac{2 u \sin \theta}{g} \times u \cos \theta\)

\(R=T \times u \cos \theta\)

\(R=T \times \frac{g T \cos \theta}{2 \sin \theta}\)

\(R=\frac{g T^2}{2} \frac{1}{\tan \theta}\)

\(\tan \theta=\frac{g T^2}{2 R}\)

\(\theta=\tan ^{-1}\left(\frac{g T^2}{2 R}\right)\)