Mathematics textbooks and their potential role in supporting misconceptions

As a fundamental resource, textbooks shape the way we teach and learn mathematics. Based on examination of secondary school and university textbooks, we describe to what extent, and how, the presentation of mathematics material–in our case study, the concept of the line tangent to the graph of a function–could contribute to creation and strengthening of students’ misconceptions. Our findings, roughly classified in several categories, raise awareness of non-obvious problems that need to be addressed when teaching calculus.