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
This introduction covers The Transversal Detective within Angles in Parallel Lines for GCSE Mathematics. Revise Angles in Parallel Lines in Geometry & Measures for GCSE Mathematics with 12 exam-style questions and 3 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 1 of 9 in this topic. Use this introduction to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Angles in Parallel Lines
Two parallel lines are cut by a transversal. Which statement about alternate angles is correct?
State the THREE angle rules that apply when a transversal crosses two parallel lines. For each rule, state whether the angles are equal or supplementary.
Quick recall flashcards
Alternate Angles
Z-shape on parallel lines, equal
Co-interior Angles
C-shape on parallel lines, add to 180°