An illustration of the Fourier Series of a [math]2\pi[/math] periodic function. The user can enter his/her own function, or choose one from a drop-down menu. Fourier coefficients are approximated through a discrete Fourier transform (DFT).
[b]Technical comment:[/b] The DFT and its inverse are computed in JavaScript (directly from the definition: no FFT!).
The same result could be achieved (in an even simpler way) by using list commands...but the resulting applet is slow as hell on tablets and phones!