This paper describes a study in which we investigated relationships between defining mathematical concepts--increasing and decreasing infinite sequences--explaining their meanings and classifying consistently with formal definitions. We explored the effect of defining, explaining or studying a definition on subsequent classification, and the…

Sarah Black wanted to remedy Year 9's lack of knowledge about nineteenth-century politics. With just five lessons to work with, she decided to devise a sequence on Gladstone and Disraeli, shaping the sequence with an enquiry question that invited argument about change and continuity. Black analyses the status and function of different layers of…