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Sinc function is a simple special function given by formula sin(x)/x on **R**\{0}
and sinc(0)=1. As we see the only difference sinc(x) from sin(x)/x is that
sinc(x) is defined at zero whereas sin(x)/x is not. The graphs of sinc can be
easy obtained in Math Center
Level 1, for example:

As we see the graph is smooth everywhere. The sinc function is also smooth in mathematical sense, that is has derivatives of all orders. Let's show that sinc(x) is continuous at zero. By l'Hôpital's rule limit of sin(x)/x at zero is equal to limit of derivative(sin(x))/derivative(x) at zero, that is cos(0)/1=1.

The normalized sinc function is similar to sinc(x) and is given by formula
sin(πx)/(πx) on **R**\{0} and sinc(0)=1. Compare graphs of sinc function and
normalized sinc function:

Graphs of two first derivatives can be obtained in Math Center Level 2 :

Apply AntiAlias and HighQuality:

Sinc function can be calculated with help of Scientific Calculator Precision 81 .

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