Sine waveform approximated with 3 Bezier curves. We say approximated because only the sine function can produce an accurate sine curve. And that, in an abstract mathematical world! If you use a sine function on a computer, its accuracy will depend on the largest and the smallest numbers you can represent on that computer. The greater this range, more accurate the sine function. But that is not the end of the story. The nature of digital audio is such that the digital sine waveform will be more accurate at low frequencies and very inaccurate at very high frequencies.
Fast Fourier Transform (FFT) of the Bezier sine waveform. Only the fundamental frequency is present. This is an important result because it doesnt matter if we use Bezier curves or the sine function to make the sine waveform, the FFT is going to be the same and so we will hear the same sound.