Proof in Swedish Upper Secondary School Mathematics Textbooks - the Issue of Transparency

We have investigated proof in two sets of commonly used Swedish upper secondary school mathematics textbooks. The frequency of proof items is low in each mathematical topic, even in the domain of geometry where pupils traditionally have learned proof. We explore the proof items with respect to different aspects of proof and discuss how they relate to students’ access to proof. We show with some examples how proof often exists invisible in the textbooks and discuss the difficulty of giving a correct definition of proof at upper secondary school level.