The Law of Cosines is a law that features in geometry and is often used to find the length of an unknown side of a triangle when the length of two sides of the triangle and the measure of the angle they form are known. This angle is called the included angle.
Knowing two sides and the included angle is referred to as SAS. The triangles given are not right triangles.
This document gives sufficient examples about this concept. It also discusses the rules used to solve the triangle.