This example is a triangle wave. Adjusting the Number of Terms slider will determine how many terms are used in the Fourier expansion (shown in red). Move the mouse over the white circles to see each term's contribution, in yellow. You can also modify the function with the mouse.
This applet has sound if you are using java 2. Click the Sound checkbox to hear the wave. It sounds very similar to a sine wave (since higher harmonics are not very strong).
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