Fourier representation of the Dirac delta function
= Fourier representation of the Dirac delta function
{title2=$\delta(x)=\frac1{2\pi}\int_{-\infty}^{\infty}e^{ikx}\,dk$}
The identity
$$
\delta(x)=\frac1{2\pi}\int_{-\infty}^{\infty}e^{ikx}\,dk
$$
is interpreted distributionally: symmetric frequency cutoffs give $\sin(nx)/(\pi x)$, which converge to the Dirac delta function.