# A triangle has sides A, B, and C. Sides A and B are of lengths #1# and #7#, respectively, and the angle between A and B is #(2pi)/3 #. What is the length of side C?

##### 1 Answer

Jan 8, 2016

#### Explanation:

First of all let me denote the sides with small letters

Let me name the angle between side "a" and "b" by

Note:- the sign

We are given with

It is given that

Using Law of Cosines