Book:Nasir al-Din al-Tusi/Kitāb al-Shakl al-Qattā

Subject Matter

 * Spherical Trigonometry

Contents
A five volume summary of trigonometry:


 * The first extant exposition of the whole system of plane and spherical trigonometry
 * The first work in which all six cases for a right-angled spherical triangle are set forth


 * Contains the famous Law of Sines:
 * $\dfrac a {\sin A} = \dfrac b {\sin B} = \dfrac c {\sin C}$