Parallel lines: tests and properties

Overview

Drag a transversal and compare corresponding, alternate interior, and consecutive interior angles.

Explanation

When parallels are cut by a transversal: corresponding angles equal, alternate interior equal, consecutive interior supplementary.
Any one of these can prove lines parallel.
Properties go “parallel → angles”; tests go “angles → parallel”.

How to use

Drag the intersection or angle slider; switch which angle pair you highlight.

Knowledge points

• Parallel lines
• Angles