# A triangle has sides A, B, and C. Sides A and B are of lengths #8# and #1#, respectively, and the angle between A and B is #(5pi)/8 #. What is the length of side C?

##### 1 Answer

Jan 27, 2018

#### Explanation:

We have two lengths and the angle between them. As such, to determine length C (the opposite length) we must use the law of cosines, in our case that will be:

where

Plugging in the numbers gives us:

So: