A) $ \frac{n}{2n^{2}+1} $
B) $ \frac{n}{n^{2}-1} $
C) $ \frac{n}{n^{2}+1} $
D) $ \frac{n^{2}-1}{n^{2}+1} $
Correct Answer: A
$ \Rightarrow $ $ \frac{\tan \alpha +\tan \beta }{1-\tan \alpha tan\beta }=\frac{1}{n} $
$ \Rightarrow $ $ n,(\tan \alpha +\tan \beta )=1-\tan \alpha \tan \beta $
$ \Rightarrow $ $ n,tan\alpha +\tan \alpha \tan \beta =1-n\tan \beta $
$ \Rightarrow $ $ \tan \alpha =\frac{1-n\tan \beta }{n+\tan \beta }=\frac{1-\frac{1}{2}}{n+\frac{1}{2n}}=\frac{n}{2n^{2}+1} $