Answer
$-2 \sin{4x} \sin{x}$
Work Step by Step
$\cos{\alpha} -\cos{\beta} = -2 \sin{(\dfrac{\alpha+\beta}{2})} \sin{(\dfrac{\alpha-\beta}{2})} $
$\cos{5x} - \cos{3x} = -2 \sin{4x} \sin{x}$
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