SOLUTION: So, I'm trying to get x-5 out of this equation sin(x/2)-sin(5/2). In order to solve a much larger equation. So, how does if factor?

We need a formula for .  I don't know one right
off, so let's derive one using the common ones that everybody knows:

, add and subtract 







1)   

If we were to interchange A and B in the above and go through the same steps
we'll get the same result with A and B switched:



Use the fact that  and  to get the A's and
B's in alphabetical order:



2)   

Now we subtract equation 2) from equation 1) and we get

  

That's the formula we need.  Maybe you already studied it and didn't
have to derive it.

Let  and 
Then  and 



becomes



or



which is a factored form.

Edwin