The value of the expression \(\tan \left(\frac{1}{2} \cos^{−1} \frac{2}{\sqrt{5}}\right)\) is
\(\rm\left[\right. Hint \left.: \tan \frac{\theta}{2}=\sqrt{\frac{1−\cos \theta}{1+\cos \theta}}\right]\)
1
2 + \(\sqrt{5}\)
2
\(\sqrt{5}\) − 2
3
\(\frac{\sqrt{5}+2}{2}\)
4
5 + \(\sqrt{2}\)