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

  • Classifying Triangles
  • အခြေခံ data အခေါ်အဝေါ်များ
  • z`]]
  • Trammel of Archimedes Art
  • Regular Polygons and Equivalent Triangles

Discover Resources

  • SOH
  • Vertical Angles Exploration (2)
  • Copia de Copia de Copia de Graphing Linear Equations in 2 Unknowns
  • THE SPACE-TIME UNIT CIRCLE

Discover Topics

  • Scalene Triangles
  • Solids or 3D Shapes
  • Exponential Functions
  • Linear Functions
  • Straight Lines
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®