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TS EAMCET · Maths · Three Dimensional Geometry

A line \(L\) is parallel to both the planes \(2 x+3 y+z=1\) and \(x+3 y+2 z=2\). If line \(L\) makes an angle \(\alpha\) with the positive direction of X-axis, then \(\cos \alpha=\)

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

Answer & Solution

Correct Answer

(A) \(\frac{1}{\sqrt{3}}\)

Step-by-step Solution

Detailed explanation

Line parallel to both planes will be perpendicular to Angle with \(X\) axis \(=\alpha\) \[ \begin{aligned} & \therefore \quad \cos \alpha=\frac{3}{\sqrt{3^2+(-3)^2+3^2}}=\frac{3}{3 \sqrt{3}} \\ & \therefore \quad \cos \alpha=\frac{1}{\sqrt{3}} . \end{aligned} \]