**This is an ‘always, sometimes, never true’ activity using dynamic geometry software to explore the properties of shapes.**The activity will help pupils to focus on strengthening geometrical reasoning, leading towards a deeper understanding of proof.

Year 9 Objectives covered:

- Solve problems using properties of angles, of parallel and intersecting lines, and of triangles and other polygons, justifying inferences and explaining reasoning with diagrams and text
- Pose questions and make convincing arguments to justify generalisations or solutions
- Recognise the impact of constraints or assumptions

- Distinguish between practical demonstration and proof in a geometrical context
- Examine and refine arguments, conclusions and generalisations
- Produce simple proofs

- Prove and use facts about angles in a circle
- Show step-by-step deduction in solving more complex geometrical problems
- Make progress by exploring mathematical tasks, developing and following alternative approaches
- Examine and extend generalisations
- Support assumptions by clear argument and follow through a sustained chain of reasoning, including proof

The activity has opportunities for:

- Pupils to focus on strengthening their geometrical reasoning
- Pupils to produce simple proofs
- Whole class teaching
- Paired work
- Independent use of ICT
- Discussion and reflection

**Download resources**