Ibn Yunus(redirected from Abul al-Hasan ben Ahmad)
Born 950; died 1009. Arab astronomer.
Ibn Yunus conducted extensive astronomical observations at an observatory near Cairo and compiled astronomical tables of the motion of the sun, moon, and planets, which for about two centuries were the best tables of their kind. He also compiled trigonometric tables. Ibn Yunus refined the values of the precessional constant and the angle of inclination of the ecliptic to the equator. He perfected the methods of the solution of plane and spherical triangles (the method of auxiliary angles).