# Formula Law of Cosine for a General Triangle Third side length    First side length    Second side length    Angle

## Third side length

Unit
The length of the third side of the triangle.

## First side length

Unit
The length of the first side of the triangle.

## Second side length

Unit
The length of the second side of the triangle.

## Angle

Unit
This angle is opposite the side $$c$$. So the angle between the sides $$a$$ and $$b$$. If $$\gamma ~=~ 90^{\circ}$$, the cosine term is dropped and the Pythagorean theorem remains.