Question

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

• A. $\frac { 2 } { 7 } , \frac { 3 } { 7 } , \frac { 6 } { 7 }$
• B. 2, 3, 6
• C. $\frac { 2 } { 11 } , \frac { 3 } { 11 } , \frac { 6 } { 11 }$
• D. None of these

Answer 1

Answer: (A)

$\frac { 2 } { 7 } , \frac { 3 } { 7 } , \frac { 6 } { 7 }$

Answer 2

Direction cosines $= \left( \frac { 4 } { \sqrt { 16 + 36 + 144 } } , \frac { 6 } { 14 } , \frac { 12 } { 14 } \right)$

or $\left( \frac { 2 } { 7 } , \frac { 3 } { 7 } , \frac { 6 } { 7 } \right)$ .