#### Answer

$\displaystyle \frac{5}{2}\cos 5x+\frac{5}{2}\cos x$

#### Work Step by Step

Product-to-Sum:
$\cos A \displaystyle \cos B=\frac{1}{2}[\cos(A+B)+\cos(A-B)]$
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$ 5\cos 3x \cos 2x=$
$=\displaystyle \frac{5}{2}[\cos(3x+2x)+\cos(3x-2x)]$
$=\displaystyle \frac{5}{2}[\cos 5x+\cos x]$
$=\displaystyle \frac{5}{2}\cos 5x+\frac{5}{2}\cos x$