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

  • רישום חופשי
  • Angle Bisector: Quick Warm Up Questions
  • seo tool
  • Text with alpha background color
  • Parabola - Write the Equation - Practice

Discover Resources

  • Morley´s Theorem
  • Puzzles of Pythagoras' theorem
  • parabolic Coaxial Family 2
  • Four Roles of Government
  • Rational Function

Discover Topics

  • Parabola
  • Rhombus
  • Power Functions
  • Incircle or Inscribed Circle
  • Sphere
AboutPartnersHelp Centre
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®