Sinc interpolation
Function approximation

We've seen that it's possible to efficiently approximate a smooth function from an equidistant sample over an interval, with algebraic convergence in general, and even exponential convergence if f is both periodic and analytic. We will now see that periodicity is not necessary for this if f is defined on any $ℝ$ and decays sufficiently rapidly to infinity.

The formula (41) can also be written as