 In 1342, Levi ben Gershon, known as Gersonides, wrote "On Sines, Chords and Arcs", in particular proving the sine law for plane triangles and giving five-figure sine tables.A simplified trigonometric table, the ""toleta de marteloio"", was used by sailors in the Mediterranean Sea during the 14th-15th Centuries to calculate navigation courses.It is described by Ramon Llull of Majorca in 1295, and laid out in the 1436 atlas of Venetian captain Andrea Bianco.