When confronted by a periodically varying function, the standard approach is to employ Fourier series, a form of analysis that uses sinusoidal functions as a basis set, having frequencies that are zero, one, two, three, etc. times the frequency of a particular fundamental cycle. These multiples are called harmonics of the fundamental frequency, and the process is termed harmonic analysis. If the basis set of sinusoidal functions suit the behaviour being modelled, relatively few harmonic terms need to be added. Orbital paths are very nearly circular, so sinusoidal variations are suitable for tides.
When confronted by a periodically varying function the standard approach is to employ Fourier series a form of analysis that uses sinusoidal functions as a basis set having frequencies that are zero one two three etc times the frequency of a particular fundamental cycle These multiples are called harmonics of the fundamental frequency and the process is termed harmonic analysis If the basis set of sinusoidal functions suit the behaviour being modelled relatively few harmonic terms need to be added Orbital paths are very nearly circular so sinusoidal variations are suitable for tides