Many studies argue that dynamic features of the artefact Cabri may function as instruments of semiotic mediation. Our study is situated in this perspective and aims to observe the impact of the use of the technological artefact Cabri in a teaching experiment that introduces the notion of a trigonometry function, through the articulation of the geometric and functions domains. This paper focuses on the potentialities provided by the Dragging tool, Measurement tool and Trace tool as semiotic mediators. The paper also explores the role of the situation "a rope on a wheel" in students' meaning making processes of trigonometric functions. Student-teacher discourse is used to identify target concept related teacher and student verbal signs, both simple signs and complex signs, including characterisations, definitions, interpretations and instantiations. The use of these signs illustrates that if conceptual development stagnates the teacher recurs to simple signs and guides the discourse to the whole spectrum of complex signs. The artefact Cabri supports such conceptual discourse because of its dynamic features as compared to paper-and-pencil methods.