I am studying for a quiz tomorrow and one of the sections I am studying involves rewriting quantities as algebraic expressions of $x$. One of the problems I am having trouble with is:
$$\sin (2\arccos x))$$
I know I have to use the double angle formula, but my problem is that I do not know to use the double angle formula for cos or sin. I was also wondering when would be the appropriate time to use it. I would appreciate any help!