Proof problems with diagrams for deductive guessing in secondary school mathematics Seminar

Lakatos introduced the notion of increasing content by deductive guessing as a method for dealing with counterexamples. Though this deductive guessing has not been deliberated in mathematics education research, it can be regarded as an authentic mathematical action. In this talk, I show that a certain kind of proof problems with diagrams can function as a useful task for realizing deductive guessing, based on a teaching experiment in the Grade 8 classroom with students aged 13-14.