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AP EAMCET · Maths · Three Dimensional Geometry

The direction cosines of the line making angles \(\frac{\pi}{4}, \frac{\pi}{3}\) and \(\theta\left(0 < \theta < \frac{\pi}{2}\right)\) respectively with \(\mathrm{X}, \mathrm{Y}\) and Z axes are

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

Answer & Solution

Correct Answer

(A) \(\frac{1}{\sqrt{2}}, \frac{1}{2}, \frac{1}{2}\)

Step-by-step Solution

Detailed explanation

\(l = \cos(\frac{\pi}{4}) = \frac{1}{\sqrt{2}}\) \(m = \cos(\frac{\pi}{3}) = \frac{1}{2}\) \(l^2 + m^2 + n^2 = 1 \implies (\frac{1}{\sqrt{2}})^2 + (\frac{1}{2})^2 + n^2 = 1\) \(\frac{1}{2} + \frac{1}{4} + n^2 = 1 \implies \frac{3}{4} + n^2 = 1\)…