Al-K?sh?’s novel method for the determination of the sine of one degree is one of the most significant contributions to the Islamic mathematics. He explained this method in Ris?la al-Watar wa al-Djayb (treatise on the chord and the sine) which no manuscript of it have yet been found; and therefore the attention of the history of sciences researchers has been attracted to Ris?la fi Istikhr?dj Djayb Daradja W?h?ida (treatise on the determination of the sine of one degree). This treatise is written by K??d?iz?da al-R?m?, al-K?sh?’s friend and colleague, and provides a detailed commentary on al-K?sh?’s method.
Presenting valid documents and evidences, this article aims to prove K??d?iz?da’s authorship of the aforementioned treatise.
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