A Nautical Instrument Lying of the Plane in Teaching the Concepts of Chord and Arc of Circumference

Background: This work follows in the direction of research dedicated to articulating historical instruments to teach mathematics. Objectives: To analyse the use of the instrument to find the altitude of the Sun as a didactic resource for teaching and learning the concepts of chord and arc of a circle in the education of undergraduate students in mathematics. Design: The research takes place through a university extension course that uses the theoretical and methodological foundations of the teaching guidance activity. Setting and Participants: The research environment is the training of students at the State University of Ceará. The training action was attended by 12 participants. The choice criterion was that they were studying for a degree in mathematics, and the selection took place in the order of enrollment in the activity. Data collection and analysis: From the assumptions of the teaching guidance activity, data collection was carried out with the recording of videos and audio, photographic records and students’ writings, while the analysis was based on connections and interconnections on the action of the subjects, and on the conceptual nexuses. Results: The new instrument to find the altitude of the Sun has didactic potential to work with the concepts of arc and chord of circumference because, from it, these concepts are mobilised as practice, and it is possible to see how they relate. Conclusions: The new instrument to find the altitude of the Sun can be explored in the interface between history and mathematics teaching as a resource to favour teaching and learning, whether in basic education or higher education.