Study Guides/Maths/Coincident Lines
Study Guide · Maths

What are Coincident Lines?

In geometry, coincident lines are lines that lie exactly on top of each other. Visually, they look like a single line. In algebra (Class 10 Maths), they represent a pair of linear equations that have infinitely many solutions.

Question (Click to Flip)

What are coincident lines?

Answer

Coincident lines are two or more lines that lie exactly on top of each other, sharing all their points.

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Key Facts

Coincident Lines: Lie on top of each other.

Algebraic Condition: a₁/a₂ = b₁/b₂ = c₁/c₂.

Solutions: Infinitely many.

System Type: Consistent and dependent.

Algebraic Condition

In a pair of linear equations: a₁x + b₁y + c₁ = 0 a₂x + b₂y + c₂ = 0

The lines are coincident if the ratio of all their coefficients is exactly the same: a₁/a₂ = b₁/b₂ = c₁/c₂

Properties of Coincident Lines

  1. Solutions: Because they touch at every single point, they have infinitely many solutions.
  2. Consistency: A system of equations that produces coincident lines is called a consistent and dependent system.
  3. Example: Eq 1: 2x + 3y = 5 Eq 2: 4x + 6y = 10 (Notice that Eq 2 is just Eq 1 multiplied by 2. They represent the exact same line!) Ratio: 2/4 = 3/6 = 5/10 = 1/2. Thus, they are coincident.

Comparison Summary

Type of LinesConditionSolutions
Intersectinga₁/a₂ ≠ b₁/b₂Exactly 1 solution
Parallela₁/a₂ = b₁/b₂ ≠ c₁/c₂No solution
Coincidenta₁/a₂ = b₁/b₂ = c₁/c₂Infinitely many

Questions and Answers

What are coincident lines?+

Coincident lines are two or more lines that lie exactly on top of each other, sharing all their points.

What is the condition for two lines to be coincident?+

For equations a₁x+b₁y+c₁=0 and a₂x+b₂y+c₂=0, the condition is a₁/a₂ = b₁/b₂ = c₁/c₂.

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