Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Applications of Derivatives

Question:

Equation of a line is $\frac{x-3}{2}=\frac{4-y}{3}=\frac{2-z}{4}$ then its direction cosines are :

Options:

$2,3, 4$

$2, -3, -4$

$\frac{2}{29},\frac{_3}{29}, \frac{-4}{29}$

$\frac{2}{\sqrt{29}}, \frac{-3}{\sqrt{29}},\frac{-4}{\sqrt{29}}$

Correct Answer:

$\frac{2}{\sqrt{29}}, \frac{-3}{\sqrt{29}},\frac{-4}{\sqrt{29}}$

Explanation:

The correct answer is Option (4) → $\frac{2}{\sqrt{29}}, \frac{-3}{\sqrt{29}},\frac{-4}{\sqrt{29}}$

first converting eq. to std. form

$\frac{x-3}{2}=\frac{4-y}{3}=\frac{2-z}{4}$

DR's = 2, -3, -4

DC's = $\frac{2}{\sqrt{2^2+(-3)^2+(-4)^2}},\frac{-3}{\sqrt{2^2+(-3)^2+(-4)^2}},\frac{-4}{\sqrt{2^2+(-3)^2+(-4)^2}}$

DC's = $\frac{2}{\sqrt{29}}, \frac{-3}{\sqrt{29}},\frac{-4}{\sqrt{29}}$