Question

If a straight line in space is equally inclined to the co-ordinate axes, the cosine of its angle of inclination to any one of the axes is
[MP PET 1992]

• A.
  
• B.
  
• C.
  
• D.
  

Answer 1

The correct option is C

Here, $cos\alpha =cos\beta =cos\gamma$
$\therefore 3co{s}^2\alpha =1\Rightarrow \alpha =co{s}^{-1}(\pm \frac{1}{\sqrt{3}})$.