Angles on Parallel Lines

When a transversal crosses two parallel lines it makes eight angles but only two different sizes. In NSW Year 8 maths (NESA outcome MA4‑ANG‑C‑01) corresponding and alternate angles are equal and co-interior angles add to \(180^\circ\), and each step names the pair used and the parallel lines, such as \(AB \parallel CD\).

You will find unknown angles in diagrams with one or two sets of parallel lines, solve for angles written as expressions such as \(3a\), and draw a construction line through a bend to split the angle there. You will also use angle pairs to decide whether two lines are parallel, check another student's reasons, and work with sunlight on flagpoles and the lines of a car park. It is part of Year 8 Geometry.