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Three Dimensional Geometry · Question 30

JEE Main 2026 (Online) 21st January Morning ShiftMCQEasy📈 Topic in 68% papers+4−1
1

Let ( , , ) be the co-ordinates of the foot of the perpendicular drawn from the point (5, 4, 2) on the line r = (- i + 3 j + k) + (2 i + 3 j - k). Then the length of the projection of the vector i + j + k on the vector 6 i + 2 j + 3 k is :

  1. 187
  2. 157
  3. 4
  4. 3

Answer

(1) 187

Solution

General point of the line: F(-1 + 2 , 3 + 3 , 1 - )

PF from P(5, 4, 2): (2 - 6, 3 - 1, - - 1)

PF (2, 3, -1): 2(2 - 6) + 3(3 - 1) - (- - 1) = 0

14 - 14 = 0 = 1

( , , ) = (1, 6, 0)

Projection on 6 i + 2 j + 3 k = (1)(6) + (6)(2) + (0)(3) 36 + 4 + 9 = 187

Answer: (1)

JEE Main 2026 (Online) 21st January Morning Shift

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2

Let the line L pass through the point (-3, 5, 2) and make equal angles with the positive coordinate axes. If the distance of L from the point (-2, r, 1) is 143, then the sum of all possible values of r is :

  1. 16
  2. 12
  3. 6
  4. 10
JEE Main 2026 (Online) 21st January Evening Shift
3

Let the line L1 be parallel to the vector -3 i + 2 j + 4 k and pass through the point (2, 6, 7), and the line L2 be parallel to the vector 2 i + j + 3 k and pass through the point (4, 3, 5). If the line L3 is parallel to the vector -3 i + 5 j + 16 k and intersects the lines L1 and L2 at the points C and D, respectively, then | CD |2 is equal to:

  1. 290
  2. 171
  3. 89
  4. 312
JEE Main 2026 (Online) 21st January Evening Shift
4

Let the values of for which the shortest distance between the lines x-12 = y-23 = z-34 and x- 3 = y-44 = z-55 is 1 6 be 1 and 2. Then the radius of the circle passing through the points (0, 0), ( 1, 2) and ( 2, 1) is

  1. 3
  2. 5 23
  3. 23
  4. 4
JEE Main 2025 (Online) 8th April Evening Shift
5

Let the area of the triangle formed by the lines x + 2 = y - 1 = z, x - 35 = y-1 = z - 11 and x-3 = y - 33 = z - 21 be A. Then A2 is equal to .

JEE Main 2025 (Online) 8th April Evening Shift
6

Let the line L pass through (1, 1, 1) and intersect the lines x-12 = y+13 = z-14 and x-31 = y-42 = z1. Then, which of the following points lies on the line L?

  1. (7, 15, 13)
  2. (4, 22, 7)
  3. (10, -29, -50)
  4. (5, 4, 3)
JEE Main 2025 (Online) 7th April Morning Shift
7

If the shortest distance between the lines x-12 = y-23 = z-34 and x1 = y = z-51 is 5 6, then the sum of all possible values of is

  1. 32
  2. 3
  3. -3
  4. - 32
JEE Main 2025 (Online) 7th April Morning Shift
8

If the equation of the line passing through the point (0, - 12, 0 ) and perpendicular to the lines r = ( i + a j + b k ) and r = ( i - j - 6 k ) + (-b i + a j + 5 k ) is x-1-2 = y+4d = z-c-4, then a + b + c + d is equal to :

  1. 13
  2. 14
  3. 12
  4. 10
JEE Main 2025 (Online) 7th April Evening Shift
9

Consider the lines L1: x - 1 = y - 2 = z and L2: x - 2 = y = z - 1. Let the feet of the perpendiculars from the point P(5, 1, -3) on the lines L1 and L2 be Q and R respectively. If the area of the triangle PQR is A, then 4A2 is equal to :

  1. 151
  2. 147
  3. 139
  4. 143
JEE Main 2025 (Online) 7th April Evening Shift
10

Let the shortest distance between the lines x-33 = y- -1 = z-31 and x+3-3 = y+72 = z- 4 be 3 30. Then the positive value of 5 + is

  1. 42
  2. 40
  3. 48
  4. 46
JEE Main 2025 (Online) 4th April Morning Shift
11

Let A and B be two distinct points on the line L : x - 63 = y - 72 = z - 7-2. Both A and B are at a distance 2 17 from the foot of perpendicular drawn from the point (1, 2, 3) on the line L. If O is the origin, then OA OB is equal to

  1. 49
  2. 21
  3. 47
  4. 62
JEE Main 2025 (Online) 4th April Morning Shift

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