If a line has direction ratios 2, -1, -2, determine its direction… - Vidyadip

MCQ

If a line has direction ratios $2, -1, -2,$ determine its direction cosines:

A
$\frac{1}{3}, \frac{2}{3},\frac{-1}{3}$
✓
$\frac{2}{3}, \frac{-1}{3},\frac{-2}{3}$
C
$\frac{-2}{3}, \frac{1}{3}, \frac{2}{3}$
D
None of the above

✓

Answer

Correct option: B.

$\frac{2}{3}, \frac{-1}{3},\frac{-2}{3}$

Direction cosines are.
$=\frac{2}{2^2+(-1)^2+(-2)^2},\frac{1}{2^2+(-1)^2+(-2)^2},\frac{-2}{2^2+(-1)^2+(-2)^2}$
$=\frac{2}{3}, \frac{-1}{3},\frac{-2}{3}$

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