Ibn Yunus and Mathematical Techniques

Ibn Yunus reached a high level of sophistication in spherical trigonometry. For example, his Hakimi Zij contains a table of sines for each 010° of arc, computed to 4 sexagesimal digits, where the values are rarely in error by more than +/-2 in the fourth digit (in keeping with the standard in Islamic works, the trigonometric functions used by Ibn Yunus are functions of arcs computed for radius 60). The Zij also outlines several hundred formulae for use in spherical astronomy (some of which are equivalent) and at least one numerical example is usually given for each formula.