If a line makes angle $90^\circ$, $60^\circ$ and $30^\circ$ with positive direction of $x$, $y$ and $z$ axis respectively. Find its direction cosines.

The correct answer is $0$, $\dfrac{1}{2}$, $\dfrac{\sqrt{3}}{2}$

$\alpha = 90^\circ$, $\beta = 60^\circ$, $\gamma = 30^\circ$

$cos \alpha$ = $cos 90^\circ$ = $0$

$cos \beta$ = $cos 60^\circ$ = $\dfrac{1}{2}$

$cos \gamma$ = $cos 30^\circ$ = $\dfrac{\sqrt{3}}{2}$