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Question: Answered & Verified by Expert
A plane passing though the points (0, -1, 0) and (0, 0, 1) and making an angle π4 with the plane yz+5=0, also passes through the point
MathematicsThree Dimensional GeometryJEE MainJEE Main 2019 (09 Apr Shift 1)
Options:
  • A (2, -1, 4)
  • B (2, 1, 4)
  • C (-2, -1, -4)
  • D (-2, 1, -4)
Solution:
2777 Upvotes Verified Answer
The correct answer is: (2, 1, 4)

The equation of a plane passing through a point x1, y1, z1 and having direction ratios of the normal to the plane as <a, b, c> is ax-x1+by-y1+cz-z1=0.

Thus, the equation of the plane passing through 0, -1, 0 is
ax-0+by+1+cz-0=0

ax+by+cz+b=0

It passes through 0, 0, 1

c=-b

Equation of plane is ax+by-bz+b=0   i

It makes angle π4 with plane y-z+5=0

The angle θ between the planes a1x+b1y+c1z+d1=0 and a2x+b2y+c2z+d2=0 is defined as cosθ=a1a2+b1b2+c1c2a12+b12+c12×a22+b22+c22

cosπ4=0+b+ba2+b2+b2×2

12=2ba2+2b2×2

Squaring both sides, we get

a2+2b2=4b2

a2=2b2

a=±2b

Equation of plane is ± 2bx+by-bz+b=0 

±2x+y-z+1=0

Option 2,  1, 4 satisfies the given equation.

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