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MathsMediumClass 12

Distance from Point to Plane

3D Geometry

16

JEE Qs

8%

Hard

40

min

Master the direct application of the distance formula and understand its geometric interpretation to efficiently solve problems involving perpendicular distance, foot of perpendicular, and image of a point.

๐Ÿงฎ Key Formulas

d = |Ax_1 + By_1 + Cz_1 + D| / sqrt(A^2 + B^2 + C^2)

โœ… Key Points for JEE

  • 1The given formula calculates the perpendicular distance from point (x_1, y_1, z_1) to the plane Ax + By + Cz + D = 0.
  • 2The coefficients A, B, C in the plane equation represent the direction ratios of the normal vector to the plane.
  • 3Always use the absolute value in the numerator, as distance is a non-negative quantity.
  • 4Ensure the plane equation is in the standard general form Ax + By + Cz + D = 0 before applying the formula, paying attention to the sign of D.

โš ๏ธ Common Mistakes

  • โœ•Forgetting to take the absolute value of the numerator, leading to an incorrect (negative) distance.
  • โœ•Incorrectly identifying coefficients A, B, C, D or coordinates x_1, y_1, z_1, especially with signs.
  • โœ•Making calculation errors in the denominator sqrt(A^2 + B^2 + C^2).

๐Ÿ“ Practice Questions

See all

Q4. Let P be the foot of the perpendicular from the point (1, 2, 2) on the line L : xโˆ’11 = y+1โˆ’1 = zโˆ’22 . Let the line โ†’r = (โˆ’^i + ^j โˆ’2^k) + ฮป(^i โˆ’^j + ^k), ฮป โˆˆR, intersect the line L at Q . Then 2(PQ)2 is equal to : (1) 25 (2) 19 (3) 29 (4) 27

2025ยทMCQMedium

Q16.Let a straight line L pass through the point P(2, โˆ’1, 3) and be perpendicular to the lines xโˆ’12 = y+11 = zโˆ’3โˆ’2 and xโˆ’3 1 = yโˆ’23 = z+24 . If the line L intersects the yz -plane at the point Q , then the distance between the points P and Q is : (1) โˆš10 (2) 2โˆš3 (3) 2 (4) 3

2025ยทMCQMedium

Q8. Let L1 : xโˆ’12 = yโˆ’23 = zโˆ’34 and L2 : xโˆ’23 = yโˆ’44 = zโˆ’55 be two lines. Then which of the following points lies on the line of the shortest distance between L1 and L2 ? (1) ( 143 , โˆ’3, 223 ) (2) (โˆ’53 , โˆ’7, 1) (3) (2, 3, 13 ) (4) ( 83 , โˆ’1, 13 )

2025ยทMCQHard

Q25.Let L1 : xโˆ’13 = yโˆ’1โˆ’1 = z+10 and L2 : xโˆ’22 = 0y = z+4ฮฑ , ฮฑ โˆˆR, be two lines, which intersect at the point B. If P is the foot of perpendicular from the point A(1, 1, โˆ’1) on L2 , then the value of 26ฮฑ( PB)2 is _________

2025ยทNumericalMedium

Q14.The perpendicular distance, of the line xโˆ’1 2 = โˆ’1 = z+32 from the point P(2, โˆ’10, 1), is : (1) 6 (2) 5โˆš2 (3) 4โˆš3 (4) 3โˆš5

2025ยทMCQMedium

Q3. Let the position vectors of the vertices A, B and C of a tetrahedron ABCD be ^i + 2^j + ^k,^i + 3^j โˆ’2^k and 2^i + ^j โˆ’^k respectively. The altitude from the vertex D to the opposite face ABC meets the median line segment through A of the triangle ABC at the point E . If the length of AD is โˆš110 and the volume of the 3 tetrahedron is โˆš805 , then the position vector of E is 6โˆš2 (1) 12 1 (7^i + 4^j + 3^k) (2) 12 (^i + 4^j + 7^k) (3) 1 6 (12^i + 12^j + ^k) (4) 16 (7^i + 12^j + ^k)

2025ยทMulti conceptHard

NCERT Chapters

  • Class 12 Maths Ch 11: Three Dimensional Geometry