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  1. Exams
  2. IIT JEE
  3. Mathematics
  4. Three dimensional geometry
46 marks

Three dimensional geometry

This chapter deals with direction cosines, direction ratios, equations of lines and planes, and shortest distances in three-dimensional space.

12 Topics
30h prep
1.9% subject weight
12 Topics
1

Coordinates of a point in space

2m1/10
📌 Key Formula(x, y, z) coordinates in 3D.
2

The distance between two points

2m1/10
📌 Key FormulaDistance = √[(x₂ - x₁)² + (y₂ - y₁)² + (z₂ - z₁)²]
3

Section formula

2m2/10
📌 Key FormulaInternal division: ((mx₂ + nx₁)/(m+n), (my₂ + ny₁)/(m+n), (mz₂ + nz₁)/(m+n))
4

Directions ratios and direction cosines

2m2/10
📌 Key Formulal² + m² + n² = 1, direction ratios a, b, c proportional to l, m, n: l/a = m/b = n/c = ±1/√(a²+b²+c²)
5

The angle between two intersecting lines

2m2/10
📌 Key Formulacos θ = |l₁l₂ + m₁m₂ + n₁n₂|
6

Skew lines

2m2/10
📌 Key FormulaLines not parallel and not intersecting.
7

The shortest distance between two intersecting lines and its equation

2m5/10
📌 Key FormulaShortest distance between skew lines = |(b₁×b₂)·(a₂ - a₁)| / |b₁×b₂|
8

Equations of a line in space

2m3/10
📌 Key FormulaVector form: r = a + λb, Cartesian: (x - x₁)/l = (y - y₁)/m = (z - z₁)/n
9

The intersection of a line and a plane

2m3/10
📌 Key FormulaSolve line and plane equations together to get point of intersection.
10

Coplanar lines

2m4/10
📌 Key FormulaCondition: (a₂ - a₁)·(b₁×b₂) = 0
11

Equation of a plane

2m2/10
📌 Key Formulaax + by + cz + d = 0
12

Distance of a point from a plane

2m2/10
📌 Key FormulaDistance = |ax₁+by₁+cz₁+d|/√(a²+b²+c²)