Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Three-dimensional Geometry

Question:

The projections of the line segment AB on the coordinate axes are –9, 12, -8 respectively. The direction cosines of the line segment AB are :

Options:

$-\frac{9}{17}, \frac{12}{17},-\frac{8}{17}$

$-\frac{9}{289}, \frac{12}{289},-\frac{8}{289}$

$-\frac{9}{\sqrt{17}}, \frac{12}{\sqrt{17}},-\frac{8}{\sqrt{17}}$

None of these

Correct Answer:

$-\frac{9}{17}, \frac{12}{17},-\frac{8}{17}$

Explanation:

Length of segment $AB=\sqrt{81+144+64}=17$

Thus direction cosines of AB are

$-\frac{9}{17}, \frac{12}{17}, \frac{-8}{17}$