1. How do you get from cell 1 to cell 2 and 3? (Geogebra File)
2. Do you show students the geometric form of a factored formula? Is it important that students know the connections between Geometry and Algebra in this case?
3. How might you bring this into a lesson on surface area of cylinders? Card sort? Plenary? Does it change how you teach areas of circles earlier on in the curriculum? i.e. by transforming the circle into a triangle to derive the area formula?