First- and second-grade prospective teachers reconstructing definitions of polygon diagonals

The current study examined how prospective first- and second-grade mathematics teachers define the polygon diagonals concept, how they reconstruct their definition during and following an intervention, and how their concept images develop over time. Twenty-three prospective teachers participated in the study, during which they were asked to analyze mathematical events involving a conflict that could be resolved using a precise mathematical definition of a polygon diagonal. Data were collected from prequestionnaires, postquestionnaires, and observations of class discussions. The study findings indicate that before the intervention, all participants provided incorrect definitions and struggled to identify nonprototypical examples of polygon diagonals in the prequestionnaire. However, the process of analyzing mathematical events helped the participants reconstruct their definitions of polygon diagonals and identify the critical attributes of this concept, which improved their ability to extend the concept's image to include nonprototypical examples. The participants' improved understanding was evident in the significant improvements in the postquestionnaire.