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TS EAMCET · Maths · Three Dimensional Geometry

If \(1,2,3\) and \(-1,0,1\) are the direction ratios of the rays \(\mathbf{O A}\) and \(\mathbf{O B}\) respectively, then the direction cosines of a normal to the plane \(A O B\) are

  1. A \(\frac{1}{\sqrt{3}}, \frac{1}{\sqrt{3}}, \frac{-1}{\sqrt{3}}\)
  2. B \(\frac{2}{3}, \frac{-2}{3}, \frac{1}{3}\)
  3. C \(\frac{-1}{\sqrt{6}}, \frac{2}{\sqrt{6}}, \frac{-1}{\sqrt{6}}\)
  4. D \(\frac{-3}{13}, \frac{4}{13}, \frac{12}{13}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(\frac{-1}{\sqrt{6}}, \frac{2}{\sqrt{6}}, \frac{-1}{\sqrt{6}}\)

Step-by-step Solution

Detailed explanation

DR's of a normal to the plan \(A O B\) are \[ \left|\begin{array}{rrr} \hat{\mathbf{i}} & \hat{\mathbf{j}} & \hat{\mathbf{k}} \\ 1 & 2 & 3 \\ -1 & 0 & 1 \end{array}\right|=\langle 2-0,-(1+3), 0+2> \]…