This Demonstration reconstructs Copernicus's chord (sine) table from De lateribus et angulis triangulorum [1], published by Rheticus. Rheticus (1514–1574) was a student of Copernicus (1473–1543). The book contains a table of chords (sines) for every minute of the quadrant and for a radius of , that is, using formula . So the chords were given to seven places. The differences were also calculated.