# How can vector dot products be used to prove the law of cosines?

##### 1 Answer

May 30, 2015

That's very simple, I'll show you how,

Let,

**A** + **B** = **C**

Thus, one may write,

**C**. **C** = (**A** + **B**).(**A** + **B**)

this implies, that

Thus we get,

This, is the law of cosines.