 
                 
                InterviewSolution
 Saved Bookmarks
    				| 1. | Prove that 1,1,1 cannot be direction cosines of a straight line. | 
| Answer» Sum of squares of direction cosines of a straight line is always `1`. Here, sum of squares of direction cosines ` = 1^2+1^2+1^2 = 3 ` As `3 !=1`, so `(1,1,1)` can not be direction cosines of a straight line. | |