1 Introduction
In various mathematical applications composite
functions are approximated by simpler functions that are
more suitable for further calculation [1, 2]. In that way, to
solve numerous technical and physical problems, periodic
functions need to be converted in series according to
trigonometric functions, i.e. to display them in the form of
a sum of sine and cosine functions of different amplitudes
and frequencies [3].
For solving and the analysis of alternating
electrotechnical networks it is suitable to use complex
calculation, wherein the voltage and the current are shown
by phasors. Phasors are composite numbers that are used
to display sinusoidal values in a complex plane. The
length of those vectors that rotate counter-clockwise with
angle velocity represents the maximal value of voltage or
current, while the projection of that vector (phasor) on the
vertical axis gives the current value of voltage or current.
The possibility of application of phasors in the analysis of
electrical values is directly dependent on their sinusoidal
nature. In case of presence of periodic signals that do not
have sinusoidal shape, the conversion of all nonsinusoidal
values into sinusoidal is the necessary
precondition for using complex calculation in the analysis
of alternating circuits [4]