Looking for a basic equation for a waveform?

 

OK - it's clear that you are looking at how a complex waveform can [in your example] be comprised of a fundamental plus one or more harmonics.

You ask what could be done to produce a better approximation. A better approximation of what? Are you asking is there another way to approximate (reproduce) the complex waveform from another perspective - other than the harmonic summation technique you used to produce it? There probably is - perhaps a polynomial representation - is that what you are asking?

In any case what you have as the original means of constructing the waveform must of itself be the "best" - it's not an approximation, rather it's a perfect or complete solution free of approximation errors.

 

Thanks for that