Here, a sine function is full-wave rectified, meaning that the wave becomes positive wherever it would be negative. This creates a new wave with double the frequency. You can see that after rectification, the fundamental frequency is eliminated, and all the even harmonics are present. Press Sine to get a clean sine wave, and view it or play it for comparison. Press Full Rectify to rectify it.
Next: Full-Wave Rectification of Sawtooth