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TS EAMCET · Maths · Three Dimensional Geometry

If the angle between the planes \(a x-y+3 z=2 a\) and \(3 x+a y+z=3 a\) is \(\frac{\pi}{3}\) then the direction ratios of the line perpendicular to the plane \((a+2) x+(a-4) y+2 a z=a\) are

  1. A \((2,-1,2)\)
  2. B \((2,1,-2)\)
  3. C \((2,1,2)\)
  4. D \((2,2,-1)\)
Verified Solution

Answer & Solution

Correct Answer

(A) \((2,-1,2)\)

Step-by-step Solution

Detailed explanation

\(\vec{n_1} = \langle a, -1, 3 \rangle\), \(\vec{n_2} = \langle 3, a, 1 \rangle\) \(\cos \frac{\pi}{3} = \frac{|\vec{n_1} \cdot \vec{n_2}|}{||\vec{n_1}|| \cdot ||\vec{n_2}||}\) \(\frac{1}{2} = \frac{|3a - a + 3|}{\sqrt{a^2 + 1 + 9}\sqrt{9 + a^2 + 1}}\)…