The document discusses the Law of Sines, which is a rule used to find unknown angles and sides of triangles when some combination of angles and sides are known. The Law of Sines states that the ratio of any side to its opposite angle is equal to the ratio of any other side to its opposite angle. An example problem demonstrates using the Law of Sines to solve a triangle when two angles and one side are given. Additional resources are provided to learn more about solving triangles with the Law of Sines.