Direction Cosines of Axes

Q. The direction cosines of the normal to the plane 2x + 3y - 6z = 5 are

1. $(2,3,-6)$
2. $\frac{2}{7},\frac{3}{7},-\frac{6}{7}$
3. $\frac{2}{5},\frac{3}{5},-\frac{6}{5}$
4. None of these

Q. A line makes angles $\alpha ,\beta ,\gamma$ with the co-ordinate axes. If $\alpha +\beta ={90}^{\circ }$, then $\gamma$ =

1. $0$
2. ${90}^{\circ }$
3. ${180}^{\circ }$
4. None of these

Q. The projections of a line on the co-ordinate axes are 4, 6, 12. The direction cosines of the line are

1. $\frac{2}{7},\frac{3}{7},\frac{6}{7}$
2. $2,3,6$
3. $\frac{2}{11},\frac{3}{11},\frac{6}{11}$
4. None of these