Source: wikibot/fejer-s-theorem
= Fejér's theorem
{wiki=Fejér's_theorem}
Fejér's theorem is a result in the theory of Fourier series, specifically concerning the convergence of the Fourier series of a periodic function. It states that if \\( f \\) is a piecewise continuous function on the interval \\(\[-L, L\]\\), then the sequence of partial sums of its Fourier series converges uniformly to the average of the left-hand and right-hand limits of \\( f \\) at each point.