Key learning points

1. Alternate, corresponding and co-interior angles can be identified in diagrams containing pairs of parallel lines.
2. Facts about angles in parallel lines can be used to find unknown angles.
3. Facts about angles in parallel lines can be used in succession to find multiple unknown angles.

Keywords

• Parallel - Two lines are parallel if they are straight lines that are always the same (non-zero) distance apart.

• Alternate angles - a pair of angles both between or both outside two line segments that are on opposite sides of the transversal that cuts them.

• Corresponding angles - Corresponding angles are a pair of angles at different vertices on the same side of a transversal in equivalent positions.

• Co-interior angles - o-interior angles are on the same side of the transversal line and in between the two other lines.

• Vertically opposite angles - Vertical angles are pairs of opposite angles formed when two lines intersect at a point. They are equal.

Common misconception