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Chapter 21 of 27
Formula Sheet

The Dimensional GeometryFormula Sheet

CG PET · Mathematics

All important formulas from The Dimensional Geometry for CG PET Mathematics. Quick reference for revision and problem solving.

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An illustration of a three-dimensional Cartesian coordinate system with X, Y, and Z axes, showing a point P(x, y, z) and its projections onto the coordinate planes to help visualize 3D space.
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Formula Sheet — The Dimensional Geometry

Important formulas and equations from The Dimensional Geometry for CG PET Mathematics.

Formulas — The Dimensional Geometry

Direction Cosines and Direction Ratios

l² + m² + n² = 1
Direction cosines = (±a/√(a²+b²+c²), ±b/√(a²+b²+c²), ±c/√(a²+b²+c²))
Direction ratios of line joining (x₁,y₁,z₁) and (x₂,y₂,z₂) = (x₂-x₁, y₂-y₁, z₂-z₁)

Equation of Line in Space

Cartesian form: (x-x₁)/a = (y-y₁)/b = (z-z₁)/c
Vector form: r⃗ = a⃗ + λb⃗
Line through two points: (x-x₁)/(x₂-x₁) = (y-y₁)/(y₂-y₁) = (z-z₁)/(z₂-z₁)
Parametric form: x = x₁ + at, y = y₁ + bt, z = z₁ + ct

Angle Between Two Lines

cosθ = |a₁a₂ + b₁b₂ + c₁c₂|/√(a₁²+b₁²+c₁²)√(a₂²+b₂²+c₂²)
cosθ = |l₁l₂ + m₁m₂ + n₁n₂|
cosθ = |b⃗₁ · b⃗₂|/|b⃗₁||b⃗₂|
Parallel condition: a₁/a₂ = b₁/b₂ = c₁/c₂
Perpendicular condition: a₁a₂ + b₁b₂ + c₁c₂ = 0

Shortest Distance Between Lines

d = |((b⃗₁ × b⃗₂) · (a⃗₂ - a⃗₁))|/|b⃗₁ × b⃗₂|
d = |det[x₂-x₁, y₂-y₁, z₂-z₁; a₁, b₁, c₁; a₂, b₂, c₂]|/√[(b₁c₂-b₂c₁)² + (c₁a₂-c₂a₁)² + (a₁b₂-a₂b₁)²]
d = |b⃗ × (a⃗₂ - a⃗₁)|/|b⃗|
Distance = 0

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Frequently Asked Questions

What topics are covered in The Dimensional Geometry for CG PET?
The Dimensional Geometry is an important chapter in CG PET Mathematics. It covers key concepts and formulas that are frequently tested in the exam. Key topics include: Direction Cosines and Direction Ratios, Equations of Lines in Space, Angle Between Two Lines, Shortest Distance Between Two Lines.
How important is The Dimensional Geometry for CG PET?
The Dimensional Geometry is a frequently tested chapter in CG PET Mathematics. Questions from this chapter appear regularly in previous year papers. There are 316 practice questions available for this chapter.
How to prepare The Dimensional Geometry for CG PET?
Start by understanding the core concepts, then solve practice questions. Focus on formulas and their applications. Use revision notes for quick review before the exam.

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