synthesise the shape of the original waveform from its
principal harmonics [e.g. sketch the waveforms of the harmonics on
the same time axis and add them together].



I don't have a function to work with. I have the 3 principle harmonics (the peaks.) How would I add them together to create the original waveform?

 

I would use a spreadsheet, or one of the free Matlab clones.

 

Or how about LTSpice? I synthesized the wave, and took the FFT to compare to the original.

 

Thanks! That looks similiar to my free draw sketch

 

Thanks! That looks similiar to my free draw sketch

Yes, but can free sketch do the FFT?

How did you decide what delay to put between the fundamental and the harmonics?