Al-Kashi was one of the best mathematicians in the Islamic world. He was born in 1380, in Kashan, in central Iran.

In order to determine sin 1°, al-Kashi discovered the following formula often attributed to François Viète in the 16th century.

This is just one of his amazing mathematical discoveries.

A method algebraically equivalent to Newton’s method was known to his predecessor Sharaf al-Dīn al-Tūsī. Al-Kāshī improved on this by using a form of Newton’s method to solve to find roots of *N*. In western Europe, a similar method was later described by Henry Biggs in his *Trigonometria Britannica*, published in 1633.