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

If a line makes an angle of $\pi /4$ with the positive direction of both the $x$-axis and $y$-axis,what angle does it make with the positive direction of the $z$-axis?

If the direction ratios $(d.r.'s)$ of two lines are connected by the relations $a-b+c=0$ and $a^2-b^2+2c^2=0$, and $\theta$ is the angle between these lines, then $\cos \theta = $

If $\alpha, \beta, \gamma$ are the angles made by a line with the positive directions of the $x, y, z$ axes respectively,then $\sin^2 \alpha + \sin^2 \beta + \sin^2 \gamma = \dots$

If a line makes an angle of $\frac{\pi}{3}$ with each of the $X$ and $Y$-axes,then the acute angle made by the line with the $Z$-axis is:

The direction cosines of two lines are $\langle\frac{\sqrt{3}}{2}, \frac{1}{4}, \frac{\sqrt{3}}{4}\rangle$ and $\langle-\frac{\sqrt{3}}{2}, \frac{1}{4}, \frac{\sqrt{3}}{4}\rangle$. Then the angle between the lines is equal to (in $^{\circ}$)