If a straight line is equally inclined at an angle $\theta$ with all the three coordinate axes,then $\tan \theta=$

If $\alpha, \beta, \gamma$ are the angles that a line makes with the positive direction of the coordinate axes,then $\sin^2 \alpha + \sin^2 \beta + \sin^2 \gamma = $

Consider the following statements:
Assertion $(A)$: The direction ratios of a line $L_1$ are $2, 5, 7$ and the direction ratios of another line $L_2$ are $\frac{4}{\sqrt{19}}, \frac{10}{\sqrt{19}}, \frac{14}{\sqrt{19}}$. Then the lines $L_1, L_2$ are parallel.
Reason $(R)$: If the direction ratios of a line $L_1$ are $a_1, b_1, c_1$, the direction ratios of a line $L_2$ are $a_2, b_2, c_2$ and $a_1 a_2 + b_1 b_2 + c_1 c_2 = 0$, then the lines $L_1, L_2$ are parallel. Which one of the following is true?

If a line makes angles $90^{\circ}$,$135^{\circ}$,and $45^{\circ}$ with the positive directions of $X$,$Y$,and $Z$-axes respectively,then its direction cosines are:

If the direction cosines of two lines are such that $2l + m + 2n = 0$ and $3l^2 + 5m^2 - 11n^2 = 0$,then the angle between the two lines is

If a unit vector makes angles $\frac{\pi}{4}$ with $\hat{i}$, $\frac{\pi}{3}$ with $\hat{j}$ and $\theta \in (0, \pi)$ with $\hat{k}$, then a value of $\theta$ is equal to...