Rewrite the expression in the form $A \sin(x+C)$ Rewrite the following expression in the form $A \sin(x+C)$
$$4 \sin x + 4\sqrt{3} \cos x$$
This is what I have so far, and I'm not even sure it's the right approach.  I just dont understand this concept as a whole:
$$A \cos(c)\sin(x) + A\sin(c)\cos(x)$$
$$A\cos (c)=4$$
$$A\sin (c)=4\sqrt{3}$$
$$\sin^2(x) + \cos^2(x) = 1$$  ??

rewrite your term in the form
$\sqrt{4^2+4^2\cdot 3}\left(\frac{4}{\sqrt{4^2+4^2\cdot3}}\sin(x)+\frac{4\sqrt{3}}{\sqrt{4^2+4^2\cdot3}}\cos(x)\right)$
now we have
$\cos(\phi)=\frac{4}{\sqrt{4^4+4^2\cdot 3}}$ and 
$\sin(\phi)=\frac{4\sqrt{3}}{\sqrt{4^2+4^2\cdot3}}$
