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Three Dimensional Geometry · Question 38

JEE Main 2025 (Online) 7th April Evening ShiftMCQMedium📈 Topic in 68% papers+4−1
1

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

Answer

(2) 147

Solution

L1 passes through (1, 2, 0) and L2 through (2, 0, 1); both have direction ratios (1, 1, 1).

Foot Q on L1: take Q = (1 + t, 2 + t, t).

PQ = (t - 4, t + 1, t + 3) and PQ (1, 1, 1) = 0

3t = 0 t = 0, so Q = (1, 2, 0)

Foot R on L2: take R = (2 + s, s, 1 + s).

PR = (s - 3, s - 1, s + 4) and PR (1, 1, 1) = 0

3s = 0 s = 0, so R = (2, 0, 1)

PQ = -4 i + j + 3 k, PR = -3 i - j + 4 k

PQ PR = vmatrix i & j & k \ -4 & 1 & 3 \ -3 & -1 & 4 vmatrix = 7 i + 7 j + 7 k

A = 12 | PQ PR | = 7 32

4A2 = 4 1474 = 147

Answer: (2)

JEE Main 2025 (Online) 7th April Evening Shift

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2

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
3

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
4

Let A be the point of intersection of the lines L1: x-71= y-50= z-3-1 and L2: x-13= y+34= z+75. Let B and C be the points on the lines L1 and L2 respectively such that AB=AC= 15. Then the square of the area of the triangle ABC is :

  1. 63
  2. 57
  3. 60
  4. 54
JEE Main 2025 (Online) 4th April Evening Shift
5

Let the values of p, for which the shortest distance between the lines x+13= y4= z5 and r=(p i+2 j+ k)+ (2 i+3 j+4 k) is 1 6, be a, b, (a<b). Then the length of the latus rectum of the ellipse x2a2+ y2b2=1 is :

  1. 32
  2. 9
  3. 18
  4. 23
JEE Main 2025 (Online) 4th April Evening Shift
6

Let a line passing through the point (4, 1, 0) intersect the line L1 : x-12 = y-23 = z-34 at the point A( , , ) and the line L2 : x - 6 = y = -z + 4 at the point B(a, b, c). Then vmatrix 1 & 0 & 1 \ & & \ a & b & c vmatrix is equal to

  1. 16
  2. 6
  3. 8
  4. 12
JEE Main 2025 (Online) 3rd April Morning Shift
7

Line L1 passes through the point (1, 2, 3) and is parallel to z-axis. Line L2 passes through the point ( , 5, 6) and is parallel to y-axis. Let for = 1, 2, 2 < 1, the shortest distance between the two lines be 3. Then the square of the distance of the point ( 1, 2, 7) from the line L1 is

  1. 25
  2. 32
  3. 40
  4. 37
JEE Main 2025 (Online) 3rd April Morning Shift
8

Each of the angles and that a given line makes with the positive y- and z-axes, respectively, is half of the angle that this line makes with the positive x-axis. Then the sum of all possible values of the angle is

  1. 2
  2. 3 4
  3. 3 2
JEE Main 2025 (Online) 3rd April Evening Shift
9

The distance of the point (7, 10, 11) from the line x-41 = y-40 = z-23 along the line x-92 = y-133 = z-176 is

  1. 16
  2. 12
  3. 18
  4. 14
JEE Main 2025 (Online) 3rd April Evening Shift
10

Let the vertices Q and R of the triangle PQR lie on the line x+35 = y-12 = z+43, QR = 5 and the coordinates of the point P be (0, 2, 3). If the area of the triangle PQR is mn then :

  1. 2m - 5 21 n = 0
  2. m - 5 21 n = 0
  3. 5m - 21 2 n = 0
  4. 5m - 2 21 n = 0
JEE Main 2025 (Online) 2nd April Morning Shift
11

If the image of the point P(1, 0, 3) in the line joining the points A(4, 7, 1) and B(3, 5, 3) is Q( , , ), then + + is equal to :

  1. 463
  2. 18
  3. 13
  4. 473
JEE Main 2025 (Online) 2nd April Evening Shift

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