Georg Joachim Rheticus (1514-1574), the professor of mathematics at the University of Wittenberg, was the only direct pupil Nicholas Copernicus ever had. Rheticus authored Narratio prima (1540), the first exposition of the Copernicus’s theory. Also, Rheticus persuaded Copernicus to allow the publication of his epochmaking De Revolutionibus (1543). Rheticus’s later publications, Canon doctrinae triangulorum (1551) and Opus palatinum de triangulis (co-authored with Valentinus Otho) (1596), laid the foundations for the science of trigonometry. Rheticus died in Košice, Slovakia.