Use power reducing formulas to fill in the blanks in the identity below:

$\displaystyle {{\tan}^{{4}}{\left({8}{x}\right)}}$ =

$\displaystyle -{4}{\cos{}}$( $\displaystyle {x}$) $\displaystyle \ +{\cos{{(}}}$ $\displaystyle {x}$) _____________________________________________________

$\displaystyle +{4}{\cos{}}$( $\displaystyle {x}$) $\displaystyle \ +{\cos{{(}}}$ $\displaystyle {x}$)