# A triangle has sides A, B, and C. Sides A and B are of lengths 4 and 2, respectively, and the angle between A and B is (pi)/8 . What is the length of side C?

Nov 25, 2016

$\text{C} = 2.3$

#### Explanation:

In order to find out the length of side C, we need to use the cosine rule:

$\text{C"^2="A"^2+"B"^2-2"AB"cos"c}$

${\text{C}}^{2} = {4}^{2} + {2}^{2} - 2 \times 4 \times 2 \times \cos \left(\frac{\pi}{8}\right) = 5.2$

$\text{C} = \sqrt{5.2} = 2.3$

And this is how your triangle (almost) looks like: