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MHT CET · Maths · Three Dimensional Geometry

The angle between the lines whose direction cosines are \(\frac{-\sqrt{3}}{4}, \frac{1}{4}, \frac{-\sqrt{3}}{2}\) and \(\frac{-\sqrt{3}}{4}, \frac{1}{4}, \frac{\sqrt{3}}{2}\) is

  1. A \(90^{\circ}\)
  2. B \(120^{\circ}\)
  3. C \(45^{\circ}\)
  4. D \(30^{\circ}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(120^{\circ}\)

Step-by-step Solution

Detailed explanation

\(\cos\theta = l_1l_2 + m_1m_2 + n_1n_2\) \(\cos\theta = \left(\frac{-\sqrt{3}}{4}\right)\left(\frac{-\sqrt{3}}{4}\right) + \left(\frac{1}{4}\right)\left(\frac{1}{4}\right) + \left(\frac{-\sqrt{3}}{2}\right)\left(\frac{\sqrt{3}}{2}\right)\)