Must prove using different identities that the left side equals the right side, meaning you don't change the right side at ALL
I tried using double angle identities after factoring it (Difference of squares right?) But it didnt seem to work?
Any ideas?
This is just the composite angle formula for the cosine of twice an angle. Don't let the confuse you. They are using it as the argument on all the functions, so it's equivalent to just x. So this is actually very simple. The function:
Can be substituted into the left side of the euqation, to obtain the right side.