Straight Lines notes
OpenThe 4 formulas you need for Straight Lines, on one page.
For explanations and lectures, see the full topic page. Then test yourself with 9 JEE Main 2026 PYQs.
Maths · printable
Straight Lines: One-Page Formula Sheet
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Last updated: 26 October 2026
Formula sheet
Straight Lines formulas
Straight Lines — formula sheet
Formulas
- Slope m = (y₂ − y₁)/(x₂ − x₁)
- Distance from (x₁, y₁) to ax + by + c = 0: |ax₁ + by₁ + c|/√(a² + b²)
- tanθ = |(m₁ − m₂)/(1 + m₁m₂)|
- Distance between parallel lines: |c₁ − c₂|/√(a² + b²)
Key ideas
- Parallel lines have equal slopes; perpendicular slopes multiply to −1
- Family of lines through intersection: L₁ + λL₂ = 0
- Distance of a point from a line
- Centroid, incentre, orthocentre basics
Traps to avoid
- Ignoring vertical lines (undefined slope)
- Sign errors in distance formula
- Missing the second angle bisector
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FAQs
Frequently asked questions
Where can I get a Straight Lines formula sheet PDF for free?
On this page. Use the print button and choose 'Save as PDF'.
How should I use a formula sheet?
Read it once a day for a week, then cover it and write the formulas from memory. Revise only the ones you missed.