Fourier-Series

A periodic function

 
(1)
is to be approximated by the sum of 2m trigonometrical elements and a constant element on the interval of [t0, t0+T ] (finite Fourier-Series):  
(2)
The coefficients A0, a1, a2, ..., am, b1, b2, ..., bm are the so called Fourier-coefficients.
The coefficient A0 in equation (2) is to be expected as the constant component (equivalent value) of the function f(t).
ω is the angular frequency of the fundamental wave and accordingly of the 1st harmonic.
(n = 2, 3, 4, ..., m) are the angular frequencies of the overtones and accordingly of the 2nd., 3rd., 4th. , …, n-th harmonic.
The angular frequency of the fundamental wave ω and the period duration T of the function f(t) are in coherence:
 
(3)