This article deals with the production of meanings around the right triangle during the resolution of a construction problem with GeoGebra, by pre-service mathematics teachers. Assuming a multimodal perspective of learning, we analyze the semiotic activity of the participants, from four categories that emphasize the semiotic and embodied nature of thinking in geometry. We conclude that the explanation of a construction procedure with GeoGebra is linked to the understanding of the geometric object to be built, due to the workspace used and the teacher educator plays an important role for achieving this understanding.