complex Fourier-Series  

A equivalent representation of the Fourier Series (equation 15) is the approach

(16)
of the decomposition using Euler's formula  

 
one obtains for the equation  
(17)
Cosine- and sine elements with the same frequency can be represented by a conjugated pair of phasors with an opposite direction of rotation.
The comparison of the approach (16) to (17) provides the coherency:
 
(18)
If the equations (13) and (14) are put into the equation (18) we obtain the algorithm for the coefficient Cn:  
(19)
For n = 0 the equation (19) merges into the equation (10) :  
(20)
This complex equation stresses the special position of the constant element A0. whitch is from now on inserted between the positive and the negative n-values and simplifies the calculation of the Fourier-coefficient Cn. This representation is very usefull for the enhancement of the treatment of Fourier series to the Fourier transformation or for system theoretical approaches.
 

beispiel 2