Sections:

Law of Sines and Law of Cosines, Page 11

Law of CosinesProtractor and a math compass

The other way in which you can solve a non-right triangle is by using the Law of Cosines.

The Law of Cosines states:

Given triangle ABC, with corresponding sides a, b, and c, the following is true:

a^2 = b^2 + c^2 - 2bc cos A; b^2 = a^2 + c^2 - 2ac cos B; c^2 = a^2 + b^2 - 2ab cos C

The Law of Cosines can be used to solve a triangle when the three sides are given, or when two sides and an included angle are given. Often, you will find that you can use either the Law of Sines or the Law of Cosines to solve a triangle.