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How can we prove: sin3A + sin2A - sinA = 4sinA .cosA/2. cos3A/2?????

plzz answer!!!!!!!!!

$To prove: sin 3A + sin 2A - sin A = 4 sin A cos \frac{A}{2} \cdot cos \frac{3 A}{2} Proof: R.H.S = 4 sin A · cos \frac{A}{2} \cdot cos \frac{3 A}{2} = 2 [2 \sin A· \cos \frac{A}{2}] \cdot cos \frac{3 A}{2} = 2 [\sin (A + \frac{A}{2}) + \sin (A - \frac{A}{2})] cos \frac{3 A}{2} = 2 [\sin \frac{3 A}{2} + \sin \frac{A}{2}) cos \frac{3 A}{2} = 2 \sin \frac{3 A}{2} \cdot \cos \frac{3 A}{2} + 2 \sin \frac{A}{2} \cdot cos \frac{3 A}{2} = \sin 3 A + [\sin (\frac{A}{2} + \frac{3 A}{2}) + \sin (\frac{A}{2} - \frac{3 A}{2})] = \sin 3 A + \sin 2 A - \sin A = L.H.S [Hence proved]$

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