Law of Sines

Theorem
For any triangle $\triangle ABC$:


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

where $a$, $b$, and $c$ are the sides opposite $A$, $B$ and $C$ respectively.

Also known as
This result is also known as the sine law, sine rule or rule of sines.

Historical Note
This was documented by in his work On the Sector Figure, part of his five-volume Kitāb al-Shakl al-Qattā (Book on the Complete Quadrilateral).