a persian treatise on the determination of the sine of one degree

dar bayan i ?istikhradj i djayb i yik daradja is a persian treatise by an anonymous author. the author’s purpose is to describe and explain a method for the determination of the sine of one degree according to ??sh ch?’s persian commentary on ulugh beg’s z?dj and ????z?da’s arabic treatise entitled ris?la fi ?istikhradj djayb daradja wahida. kad?zada’s work extant in several manuscripts is in fact a revision of the lost work of the real inventor of the method kashani(al kashi). kush ch? in his commentary explains kashan?’s method without mentioning his name. in this article dar bayan i ?istikhradj i djayb i yik daradja is rewritten based on its unique manuscript so that one can follow the traces of author’s citations from ??sh ch? and kad?zada’s works.