Three Dimensional Geometry: 2 marks Questions (CBSE Class 12)
6 different 2 marks questions on Three Dimensional Geometry from CBSE Class 12 Maths board exams 2026, newest first.
Find the co-ordinates of the point on the line r=−j^+3k^+λ(2i^−2j^+k^) such that the sum of co-ordinates is 3.
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Answer: (2,−3,4)
- A general point on the line is (2λ,−1−2λ,3+λ).
- Sum of co-ordinates: 2λ−1−2λ+3+λ=2+λ=3⇒λ=1.
- Point: (2,−3,4).
Find the co-ordinates of foot of perpendicular drawn from (0, 0, 0) to line 1x=−1y+1=−2z−3.
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Answer: (65,−611,34)
- A general point on the line is P(λ,−1−λ,3−2λ); the line's direction ratios are 1,−1,−2.
- OP⊥ line: λ(1)+(−1−λ)(−1)+(3−2λ)(−2)=0⇒6λ−5=0⇒λ=65.
- Foot of perpendicular: (65,−611,34).
Find the co-ordinates of the point on line x=2y−1=3z−2 whose y co-ordinate is 3 times the x co-ordinate.
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Answer: (1,3,5)
- A general point on the line is (λ,1+2λ,2+3λ).
- 1+2λ=3λ⇒λ=1.
- Point: (1,3,5).
If the lines 1x−3=11−y=pz+2 and 32−x=5y+1=2pz+56 are perpendicular to each other, then find the value(s) of p.
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Answer: p=±2
- In standard form the first line is 1x−3=−1y−1=pz+2: d.r. ⟨1,−1,p⟩.
- The second is −3x−2=5y+1=2pz+56: d.r. ⟨−3,5,2p⟩.
- Perpendicular: (1)(−3)+(−1)(5)+p(2p)=0, so 2p2=8.
- p=±2.
Find the vector equation of a line passing through the origin and perpendicular to both the lines r=2i^−j^+2k^+λ(3i^+4j^+2k^) and r=μ(i^−j^+k^).
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- A direction perpendicular to both is (3i^+4j^+2k^)×(i^−j^+k^).
- =i^(4+2)−j^(3−2)+k^(−3−4)=6i^−j^−7k^.
- Line through the origin: r=λ(6i^−j^−7k^).
Find the angle between the following pair of lines :
3x−2=2y+5=−61−z and
1x−7=2y=−26−z
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Answer: cos−1(2119)
- Write the lines as 3x−2=2y+5=6z−1 and 1x−7=2y=2z−6.
- Direction ratios: (3, 2, 6) and (1, 2, 2).
- cosθ=4993+4+12=2119.
- θ=cos−1(2119).
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