A sum of sinusoids is periodic only if their frequencies share a common divisor

Evidence

This principle—that the sum of the solutions is the same as the solution of the sum of the sine waves— is called superposition and is a powerful aspect of the Fourier approach. — David Howard, Jamie Angus, coustics and Psychoacoustics, 439 (#expands, via linked claim)

Categorization

  • XREF: connects to: Only a sinusoid has a single frequency; every other shape contains multiple frequencies; Superposition lets complex waveforms be solved as sums of sine wave solutions — David Howard, Jamie Angus, coustics and Psychoacoustics, 439; Any waveform can be approximated by summing orthogonal sine waves

Broader Connections