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.
๐งฎ Key Formulas
โ 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.
โ ๏ธ Common Mistakes
- โForgetting to take the absolute value of the numerator, leading to an incorrect (negative) distance.
- โIncorrectly identifying coefficients A, B, C, D or coordinates x_1, y_1, z_1, especially with signs.
- โMaking calculation errors in the denominator sqrt(A^2 + B^2 + C^2).
๐ Practice Questions
See allQ4. Let P be the foot of the perpendicular from the point (1, 2, 2) on the line L : xโ11 = y+1โ1 = zโ22 . Let the line โr = (โ^i + ^j โ2^k) + ฮป(^i โ^j + ^k), ฮป โR, intersect the line L at Q . Then 2(PQ)2 is equal to : (1) 25 (2) 19 (3) 29 (4) 27
Q16.Let a straight line L pass through the point P(2, โ1, 3) and be perpendicular to the lines xโ12 = y+11 = zโ3โ2 and xโ3 1 = yโ23 = 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) โ10 (2) 2โ3 (3) 2 (4) 3
Q8. Let L1 : xโ12 = yโ23 = zโ34 and L2 : xโ23 = yโ44 = zโ55 be two lines. Then which of the following points lies on the line of the shortest distance between L1 and L2 ? (1) ( 143 , โ3, 223 ) (2) (โ53 , โ7, 1) (3) (2, 3, 13 ) (4) ( 83 , โ1, 13 )
Q25.Let L1 : xโ13 = yโ1โ1 = z+10 and L2 : xโ22 = 0y = z+4ฮฑ , ฮฑ โR, be two lines, which intersect at the point B. If P is the foot of perpendicular from the point A(1, 1, โ1) on L2 , then the value of 26ฮฑ( PB)2 is _________
Q14.The perpendicular distance, of the line xโ1 2 = โ1 = z+32 from the point P(2, โ10, 1), is : (1) 6 (2) 5โ2 (3) 4โ3 (4) 3โ5
Q3. Let the position vectors of the vertices A, B and C of a tetrahedron ABCD be ^i + 2^j + ^k,^i + 3^j โ2^k and 2^i + ^j โ^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 โ110 and the volume of the 3 tetrahedron is โ805 , then the position vector of E is 6โ2 (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)
NCERT Chapters
- Class 12 Maths Ch 11: Three Dimensional Geometry