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

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

Published $\text {c. $1250$}$.
In English:

Treatise on the Quadrilateral


Subject Matter


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:
$\dfrac a {\sin A} = \dfrac b {\sin B} = \dfrac c {\sin C}$


Sources