This applet demonstrates Fourier series, which is a method of expressing an arbitrary periodic function as a sum of cosine terms. In other words, Fourier series can be used to express a function in terms of the frequencies (harmonics) it is composed of.
To select a function, you may press one of the following buttons: Sine, Triangle, Sawtooth, Square, and Noise. The function is displayed in white, with the Fourier series approximation in red. You can edit the function directly by clicking on it.
Index of examples.
Full screen version.
Digital Filters Applet.