Key learning points

1. By considering a number of different triangles you can demonstrate facts about the angles in triangles.
2. The interior angles of any triangle sum to 180°
3. The angle sum of triangles can be proved using angles in parallel lines.

Keywords

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

Common misconception