In this video tutorial the author shows how to use the Cosine Law. He shows how to find an angle of a triangle where he know all the sides of a triangle, using the cosine Law. He uses a lower case letter to designate a side and a capital letter to designate an angel apposite to that side. He gives the formula for the cosine law using a triangle as an example. Now he goes on and demonstrates how to use a scientific calculate. He shows how to use the degree mode in the calculator to solve these problems easily. Now he demonstrates the cosine law with an example triangle and arrives at the unknown angle of the triangle. If you are looking for a comprehensive and in depth tutorial of the Cosine law this is a good tutorial to start with.