Integrate the function `sinxsin2xsin3x`

Explanation

To integrate the function \( \sin x \sin 2x \sin 3x \), we can follow these steps:

### Step 1: Rewrite the function
We start by rewriting the function:
\[ \sin x \sin 2x \sin 3x = \sin x \cdot \sin 2x \cdot \sin 3x \]
We can express \( \sin 2x \) as \( \frac{1}{2} (2 \sin x \cos x) \) to facilitate the integration.
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