If sin^3 x sin 3x = sum_{m=0}^n c_m cos mx wh | vedclass

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(B) We know that $\sin 3x = 3 \sin x - 4 \sin^3 x$,so $\sin^3 x = \frac{1}{4}(3 \sin x - \sin 3x)$.Substituting this into the expression:$\sin^3 x \si

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$6$

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(B) We know that $\sin 3x = 3 \sin x - 4 \sin^3 x$,so $\sin^3 x = \frac{1}{4}(3 \sin x - \sin 3x)$.Substituting this into the expression:$\sin^3 x \sin 3x = \frac{1}{4}(3 \sin x - \sin 3x) \sin 3x$$= \frac{3}{4} \sin x \sin 3x - \frac{1}{4} \sin^2 3x$$= \frac{3}{8}(2 \sin 3x \sin x) - \frac{1}{8}(2 \sin^2 3x)$Using the identities $2 \sin A \sin B = \cos(A-B) - \cos(A+B)$ and $2 \sin^2 A = 1 - \cos 2A$:$= \frac{3}{8}(\cos 2x - \cos 4x) - \frac{1}{8}(1 - \cos 6x)$$= -\frac{1}{8} + \frac{3}{8} \cos 2x - \frac{3}{8} \cos 4x + \frac{1}{8} \cos 6x$Comparing this with $\sum_{m=0}^n c_m \cos mx = c_0 + c_1 \cos x + \dots + c_n \cos nx$,we see that the highest frequency term is $\cos 6x$,so $n = 6$.

If $\sin^3 x \sin 3x = \sum_{m=0}^n c_m \cos mx$ where $c_0, c_1, c_2, \dots, c_n$ are constants and $c_n \neq 0$,then the value of $n$ is

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