A new learning trajectory for trigonometric functions

Educational research has shown that many secondary school students consider the subject of trigo-nometric functions as difficult and only develop shallow and fragmented understanding. It is un-clear which of the two popular approaches to introducing trigonometry, namely the ratio method and the unit circle method, works best. In this study we propose a new framework for trigonometric understanding and a new, dynamic geometry supported trajectory for learning trigonometric func-tions. We also report on the results of a classroom case study in which the new approach has been implemented and researched. We discuss the task-related difficulties that students faced in their concept development and we describe their trigonometric understanding in terms of our framework.