If the projections of a line segment on the coordinate axes are $2, 3, 6$,find the length of the line segment.

If the projections of a line segment on the coordinate axes are $3, 4,$ and $5$,then its length is:

$A$ ray makes angles $\frac{\pi}{3}$ and $\frac{\pi}{4}$ with $Y$ and $Z$-axes respectively. Then,the value of the sine of the angle made by the ray with $X$-axis is

$A$ line makes a $45^{\circ}$ angle with the positive $X$-axis and makes equal angles with the positive $Y$-axis and $Z$-axis respectively. The sum of the three angles which the line makes with the positive $X$-axis,$Y$-axis,and $Z$-axis is: (in $^{\circ}$)

If two lines are parallel to each other,then which of the following is true? (If $(l_1, m_1, n_1)$ and $(l_2, m_2, n_2)$ are direction cosines of the two lines).

If the direction ratios of two lines are $5, -12, 13$ and $-3, 4, 5$,then the angle between them is: