# A triangle has sides A, B, and C. Sides A and B are of lengths #7# and #5#, respectively, and the angle between A and B is #(5pi)/8 #. What is the length of side C?

##### 1 Answer

#### Explanation:

Well this is a very tricky one, i wish i can draw the Triangle to explain better, but with the theory i hope you will understand..

Firstly Note that the Angle is in Radians..

If you observe closely,

**Angel between A and B is #color(white)(x)5pi/8#**

You're aware that there are only 3 angels which are

Now again; What is the Angle between

Simple, the answer is

Cause it's a Triangle so the angle is C, since it's in between the two angles..

It's just a trick to push you off course from the desired Answer..

Hence we have as follows;

Before we proceed further, remember first i said **Note that the Angle is in Radians..**

We must first convert from Radians to Degree..

**Using this formula**

Hence

Now to find **c** we shall using the **Cosine Rule Formula**

Imputing your values..