Born in Buzjan, Nishapur (now Iran), Abul Wafa flourished as a mathematician and astronomer at the observatory at Sharaf al Daula, where he was the first to build a wall quadrant (over 6 m long) to observe star positions. Best known for trigonometry, he contributed to the theory of the Moon, in which he first used the tangent function, and introduced the secant and cosecant