Show that the direction cosines of a vector equally inclined to the axes OX, OY and OZ are $\frac{\large 1}{\large \sqrt 3}, \: \frac{\large 1}{\large \sqrt 3}, \: \frac{\large 1}{\large \sqrt 3}$

Question

$\begin{array}{1 1} (A) \large(\frac{1}{\sqrt3},\frac{1}{\sqrt3},-\frac{1}{\sqrt3}) \\ (B) \large(\frac{1}{\sqrt3},-\frac{1}{\sqrt3},\frac{1}{\sqrt3}) \\ (C) \large(-\frac{1}{\sqrt3},\frac{1}{\sqrt3},\frac{1}{\sqrt3}) \\ (D) \large(\frac{1}{\sqrt3},\frac{1}{\sqrt3},\frac{1}{\sqrt3}) \end{array}$