>>2713959Well, according to Fourier analysis, every waveform can be broken down into composite sinusoids (a fundamental frequency + harmonics) so every waveform can be represented as a sum of sine waves with different amplitudes, frequencies and phases (this is what a spectrograph shows btw).
Waveforms are used in AC electrical engineering (less relevant for DC) and probably some kinds of arcane maths and physics that I've never heard of.