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JEE Mains · Maths · STD 12 - 11. three dimension geometry

Let a unit vector \(\hat{ OP }\) make angle \(\alpha, \beta, \gamma\) with the positive directions of the co-ordinate axes \(OX , OY\), \(OZ\) respectively, where \(\beta \in\left(0, \frac{\pi}{2}\right) \hat{ OP }\) is perpendicular to the plane through points \((1,2,3)\), \((2,3,4)\) and \((1,5,7)\), then which one of the following is true ?

  1. A \(\alpha \in\left(\frac{\pi}{2}, \pi\right)\) and \(\gamma \in\left(\frac{\pi}{2}, \pi\right)\)
  2. B \(\alpha \in\left(0, \frac{\pi}{2}\right)\) and \(\gamma \in\left(0, \frac{\pi}{2}\right)\)
  3. C \(\alpha \in\left(\frac{\pi}{2}, \pi\right)\) and \(\gamma \in\left(0, \frac{\pi}{2}\right)\)
  4. D \(\alpha \in\left(0, \frac{\pi}{2}\right)\) and \(\gamma \in\left(\frac{\pi}{2}, \pi\right)\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(\alpha \in\left(\frac{\pi}{2}, \pi\right)\) and \(\gamma \in\left(\frac{\pi}{2}, \pi\right)\)

Step-by-step Solution

Detailed explanation

Equation of plane :- \(\left|\begin{array}{ccc}x-1 & y-2 & z-3 \\ 1 & 1 & 1 \\ 0 & 3 & 4\end{array}\right|=0\) \(\Rightarrow[x-1]-4[y-2]+3[z-3]=0\) \(\Rightarrow x-4 y+3 z=2\) \(D.R's\) of normal of plane \( < 1,-4,3 > D.C's\) of…
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