Search
GeoGebra
  • Home
  • Resources
  • Profile
  • Classroom
  • App Downloads

Lesson 86. Properties of Parallel Lines

Author:Norm Prokup

T6-criterion for parallel lines

[bgcolor=orange] If two lines are intersected by a third line, and alternate interior (or exterior) angles are equal, then the original two lines are parallel. [/bgcolor]

New Resources

  • Cartesian Notation of a Vector
  • AI for worksheet development
  • Export grapfics view
  • The Coordinate Plane (Cartesian Plane)
  • Parallel Lines and Angles: Thinking Classroom Exploration

Discover Resources

  • Reflection of orthocentre in sides lies on the circumcentre
  • Vase
  • Angle Bisectors
  • Isosceles Triangle
  • Modul 3.6_Mira Nopitria_SD Negeri 01 Pendopo

Discover Topics

  • Quadratic Equations
  • Correlation
  • Random Variables
  • Circle
  • Sequences and Series
AboutPartnersHelp Center
Terms of ServicePrivacyLicense
Graphing CalculatorCalculator SuiteMath Resources

Download our apps here:

Download_on_the_App_Store_Badge_US-UK_RGB_blk_4SVG_092917

© 2026 GeoGebra®