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← JEE Main 2022 · 24 Jun · Shift 2
MathematicsSingle correct+4 / -1Question 15 of 90

JEE Main 2022 · 24 Jun · Shift 2, Mathematics question 15

Let the points on the plane P be equidistant from the points (−4,2,1)(-4,2,1) and (2,−2,3)(2,-2,3). Then the acute angle between the plane P and the plane 2x+y+3z=12x+y+3z=1 is

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Answer and worked solution

Official answer: C

Plane P is the perpendicular bisector plane, with normal along (2,−2,3)−(−4,2,1)=(6,−4,2)∥(3,−2,1)(2,-2,3)-(-4,2,1)=(6,-4,2)\parallel(3,-2,1).

Angle. cos⁡θ=(3,−2,1)⋅(2,1,3)1414=714=12\cos\theta=\dfrac{(3,-2,1)\cdot(2,1,3)}{\sqrt{14}\sqrt{14}}=\dfrac7{14}=\dfrac12, so θ=π3\theta=\dfrac\pi3.

(C)