The reflection of the point $(\alpha, \beta, \gamma)$ in the $XY$-plane is:

Fill in the blanks:
The coordinates of points in the $XY$-plane are of the form ...........

If the direction cosines of two lines are $(\frac{2}{3}, \frac{2}{3}, \frac{1}{3})$ and $(\frac{5}{13}, \frac{12}{13}, 0)$,then identify the direction ratios of a line which is bisecting one of the angles between them.

The direction cosines of the normal to the plane $3x + 4y + 12z = 52$ will be

If a line makes angles of measure $\frac{\pi}{6}$ and $\frac{\pi}{3}$ with $X$ and $Y$ axes respectively,then the angle made by the line with $Z$ axis is

If the direction cosines of two lines satisfy the equations $2l+m-n=0$ and $l^2-2m^2+n^2=0$, and $\theta$ is the angle between the lines, then $\cos \theta=$