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Three Dimensional Geometry — MATHS STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceMATHSThree Dimensional Geometry1 Mark
Question
If a line has direction ratios 2, -1, -2, determine its direction cosines:
  1. $\frac{1}{3}, \frac{2}{3},\frac{-1}{3}$
  2. $\frac{2}{3}, \frac{-1}{3},\frac{-2}{3}$
  3. $\frac{-2}{3}, \frac{1}{3}, \frac{2}{3}$
  4. None of the above
✓

Answer

  1. $\frac{2}{3}, \frac{-1}{3},\frac{-2}{3}$
Solution:
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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