Angles in Parallel Lines

MathematicsAQAEdexcelGCSEUnit: Geometry & Measures
Free taster
5 of 6 sections open
The basics

The Transversal Detective

The Transversal Detective

When a line crosses two parallel lines (called a transversal), it creates 8 angles. But here's the magic: there are only really 2 different angle sizes! Once you know one angle, you can work out all the others using three simple rules.

Visual: Angles in Parallel Lines

Diagram showing corresponding, alternate, and co-interior angles formed when a transversal crosses parallel lines
Spotlight
The Three Key Rules

Also called: Co-interior angles = Allied angles = Interior angles

Now try it yourself

Quiz · Question 1 of 12

Two parallel lines are cut by a transversal. Which statement about alternate angles is correct?

Tap an answer to check it

Revise every Mathematics topic, free during alpha

Angles in Parallel Lines is one of 127 topics on PrepWise — all aligned to your exam board.

Start revising free →