Question

The projection of a directed line segment on the co-ordinate axes are $12,4,3$, then the direction cosines of the line are

• A. $\frac{-12}{13},\frac{-4}{13},\frac{-3}{13}$
• B. $\frac{12}{13},\frac{4}{13},\frac{3}{13}$
• C. $\frac{12}{13},\frac{-4}{13},\frac{3}{13}$
• D. $\frac{12}{13},\frac{4}{13},\frac{-3}{13}$

Answer 1

The correct option is B $\frac{12}{13},\frac{4}{13},\frac{3}{13}$

$x=12,y=4,z=3$

Direction cosines $=\frac{x}{\sqrt{x^2+y^2+z^2}},\frac{y}{\sqrt{x^2+y^2+z^2}},\frac{z}{\sqrt{x^2+y^2+z^2}}$

$=\frac{12}{13},\frac{4}{13},\frac{3}{13}$

Hence, option 'B' is correct.