$\frac{\sin(x)}{x} \geqslant \frac{16 \pi^4}{\left(3 \pi^2+x^2\right)^2}-1$

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证明 $\forall x \in (0,\pi)$,$$\frac{\sin(x)}{x} \geqslant \frac{16 \pi^4}{\left(3 \pi^2+x^2\right)^2}-1$$

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