The law of cosines, otherwise known as the cosine formula or cosine rule, gives a formula that relates the lengths of the sides of a triangle to the cosine of one of its angles.

$c^2\=a^2\+b^2-2\cdot a\cdot b\cdot \cos \left(\mathrm{\γ}\right)$

where $\mathrm{\γ}$ is the angle between the sides $a$ and $b$, with opposite side $c$.

The following interface solves for either the value of $c$ or $\mathrm{\γ}$.