$\tan^{-1} (\frac{1}{4}) + \tan^{-1} (\frac{2}{9})$ is equal to :

Question

( A ) $\frac{1}{2} \cos^{-1} (\frac{3}{5})$
( B ) $\frac{1}{2} \tan^{-1} (\frac{3}{5})$
( C ) $\tan^{-1} (\frac{1}{2})$
( D ) $\frac{1}{2} \sin^{-1} (\frac{3}{5})$