The article analyses the contents of chapters XII, XIII and XIV of Nicolaus Copernicus’ first book De revolutionibus orbium coelestium. These chapters contain the trigonometric material on which the astronomer based all considerations about heliocentrism. In chapter XII, he built “chords of a circle” tables, which today we would call sinus tables. Chapters XIII and XIV dealt with the solu- tion of flat and spherical triangles. In this paper, this mathematical apparatus has been analysed from a contemporary point of view, using modern symbols and terminology. The analysis was car- ried out on the reception of Copernicus mathematics in school teaching on the Polish territories from the 16th to the 21st century.