# Why is the cosine of an obtuse angle negative?

##### 1 Answer

Nov 22, 2015

Draw the cosine function between 0 and 180 degrees and you will learn why angles **negative**

#### Explanation:

Here is the graph of cosine:

As you can see, once the cosine function is **greater than 90** degrees, the value becomes **negative** .

**Between 0 and 90 degrees** , cosine is **positive** .

hope that helped