رساله اي فارسي درباره محاسبه جيب يك درجه

A Persian Treatise on the Determination of the Sine of One Degree

Dar Bayan-e Estekhradj-e Djayb-e Yek Darad[e is a Persian treatise by an anonymous author. The authorʹs purpose is to describe and explain a method for the determination of the Sine of one degree according to Kushchiʹs Persian commentary on Ulugh Begʹs Zidj, and Kadizadaʹs Arabic treatise entitled Risala fi Istikhradj Djayb Daradjah Wahidah. Kadlzadaʹs work, extant in several manuscripts, is, in fact, a revision of the lost work of the real inventor of the method, Kashani (al-Kashi). Kushchi in his commentary explains Kashaniʹs method, without mentioning his name. In this article, Dar Bayan-e Estekhradj-e Djayb-e Yek Daradje is rewritten based on its unique manuscript, extant in Berlin, so that one can follow the traces of authorʹs citations from Kushchi and Kadizadaʹs works.