Are you sure you didn't mean ? That's a much more interesting question. As topsquark says, your equation is just a matter of combining those two " terms.
To solve , use the identity sin(A+B)= sin(A) cos(B)+ cos(A) sin(B). That would be the same as the previous equation if a= sin(A) and b= cos(A). The problem with that is that we would have to have which is not, in general, true. We can fix that factoring out. That is, we write the equation as
so that
So that now
Now, we can let and so that the equation can be written
then