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CUET · MATHS · PYQ PAPER 2025

The direction cosines of a line equally inclined with the co-ordinate axes are :

  1. A (1, 1, 1)
  2. B \(\left(\frac{1}{3}, \frac{1}{3}, \frac{1}{3}\right)\)
  3. C \(\left( \pm \frac{1}{\sqrt{3}}, \pm \frac{1}{\sqrt{3}}, \pm \frac{1}{\sqrt{3}}\right)\)
  4. D \(\left(\frac{1}{\sqrt{2}}, \frac{1}{\sqrt{2}}, \frac{1}{\sqrt{2}}\right)\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(\left( \pm \frac{1}{\sqrt{3}}, \pm \frac{1}{\sqrt{3}}, \pm \frac{1}{\sqrt{3}}\right)\)

Step-by-step Solution

Detailed explanation

\(l=m=n=\cos\alpha\) \(l^2+m^2+n^2=1\) \(3\cos^2\alpha=1\) \(\cos\alpha=\pm\frac{1}{\sqrt{3}}\) Direction cosines are \(\left( \pm \frac{1}{\sqrt{3}}, \pm \frac{1}{\sqrt{3}}, \pm \frac{1}{\sqrt{3}}\right)\)
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