# A triangle has sides A, B, and C. Sides A and B are of lengths 5 and 4, respectively, and the angle between A and B is (11pi)/12 . What is the length of side C?

Apr 15, 2018

8.9

#### Explanation:

Using ${c}^{2} = {a}^{2} + {b}^{2} - 2 b c$CosC

${c}^{2} = 25 + 16 - 40 C o s$$\left(\frac{11 \pi}{12}\right)$

${c}^{2} = 41 - 40 C o s$$\left(\frac{11 \pi}{12}\right)$

${c}^{2} = 79.63703305$

$c = 8.923958373$