Answer
See the steps.
Work Step by Step
$RHS = 4 \sin{A}\cos^3{A} - 4 \cos{A} \sin^3{A} $
$RHS= 4 \sin{A}\cos{A} (\cos^2{A} - \sin^2{A})$
$RHS = 2 \sin{2A} \cos{2A} = \sin{4A} = LHS$
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