Developing an analytical tool of the processes of justificational mediation

Within the Instrumental Approach (IA) the newly developed notion of justificational mediation (JM) describes mediations that aim at establishing truth of mathematical statements in the context of CAS-assisted proofs in textbooks. Here we study JM with the intent to broaden the notion to the context of informal justification processes of early secondary students interacting with GeoGebra. Seeing JM as a process that has the objective of changing the status of a claim, we use Toulmin’s model and combine it with the IA to unravel the structure of the process through an analytical tool. The study is part of a broader project on the interplay between reasoning competency and GeoGebra with lower secondary students.