# sinc函数

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In mathematics, physics and engineering, the sinc function, denoted by $$sinc(x)$$, has two forms, normalized and unnormalized.

In mathematics, the historical unnormalized sinc function is defined for $$x \neq 0$$ by $$sinc(x)=\cfrac{\sin{x}}{x}$$

Alternatively, the unnormalized sinc function is often called the sampling function, indicated as Sa(x).

In digital signal processing and information theory, the normalized sinc function is commonly defined for $$x \neq 0$$ by $$sinc(x)=\cfrac{\sin{\pi x}}{\pi x}$$

In either case, the value at $$x = 0$$ is defined to be the limiting value:

$$\lim_{x\rightarrow 0}=\cfrac{\sin{ax}}{ax}=1, a\neq 0$$

sinc函数图像： -- EOF --

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