For an infinite number of equally spaced
samples, with spacing
, the Lagrange-interpolation basis
polynomials converge to shifts of the sinc function, i.e.,
Alternate Proof: Every analytic function is determined by its zeros and its
value at one nonzero point. Since
is zero on all the
integers except 0, and since
sinc
, it therefore coincides with
the Lagrangian basis polynomial for
and
.