The line of shortest distance between the lines x-2 0= y-1 1= z 1 and x-3 2= y-5 2= z-1 1 makes an angle of sin^-1(√ 2 27) with the plane…
JEE Main 2022 — Mathematics Vectors & 3D Geometry
2022integermedium
The line of shortest distance between the lines 0x−2=1y−1=1z and 2x−3=2y−5=1z−1 makes an angle of sin−1(272) with the plane P:ax−y−z=0,(a>0). If the image of the point (1,1,−5) in the plane P is (α,β,γ), then α+β−γ is equal to _____ .
Official previous-year question
Held on 25 Jul 2022 · Verified 6 Jul 2026.
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Solution
Given lines, 0x−2=1y−1=1z and 2x−3=2y−5=1z−1
Now direction ratio of line of shortest distance will be,
∣i^02j^12k^11∣=−i^+2j^−2k^
Now given angle between line and plane is sin−1272=α, so sinα=272
Now direction ratio of normal to plane is (a,−1,−1)
So, sinα=∣4+4+1a2+1+1−a−2+2∣=332
⇒3∣a∣=2a2+2
⇒3a2=2a2+4
⇒a2=4
⇒a=2(asa>0given)
Now equation of plane will be 2x−y−z=0 and image of point (1,1,−5) will be,
2x−1=−1y−1=−1z+5=−222+12+12(2−1+5)
⇒2x−1=−1y−1=−1z+5=−2
⇒x=−3,y=3,z=−3
So, α=−3,β=3,γ=−3
So, α+β−γ=−3+3+3=3
Note: This question was bonus in JEE mains 25th july 2022 paper, we have done some modification to the original question.
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