Find , when

y = sin x sin 2x sin 3x sin 4x

Let y = sin x sin 2x sin 3x sin 4x


Take log both sides:


log y = log (sin x sin 2x sin 3x sin 4x)


log y = log (sin x ) + log (sin 2x) + log (sin 3x) + log (sin 4x)



Differentiating with respect to x:














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