Key learning points

1. The sum of angles at a point can be used to find missing angles.
2. The angle sum of a straight line can be used to find missing angles.
3. Vertically opposite angles can be used to find missing angles.
4. The size of missing angles can be justified by using known facts.

Keywords

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

• Vertex - A vertex is the point where two or more line segments meet. The plural is vertices.

• Similar - Two shapes are similar if the only difference between them is their size. Their side lengths are in the same proportions.

• Supplementary angles - Supplementary angles are a pair of angles that sum to 180°.

• Conjugate angles - Conjugate angles are a pair of angles that sum to 360°.

Common misconception