Question 1094046
.
On cosine law see the lessons

&nbsp;&nbsp;&nbsp;&nbsp;-<A HREF=http://www.algebra.com/algebra/homework/Trigonometry-basics/Proof-of-the-Law-of-Cosines-revisited.lesson>Proof of the Law of Cosines revisited</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Trigonometry-basics/Solve-triangles-using-Law-of-Cosines.lesson>Solve triangles using Law of Cosines</A>

in this site.