The representation of a time domain signal by a summation of sine or
cosine components is usually referred to as the spectrum of
the waveform. It is traditional to draw the spectrum as discrete lines on a graph, with
the position of the lines on the x-axis representing the frequency of the component, and
the height of the line representing the amplitude.
Again, it is common practice to represent only the absolute value or magnitude of each
component in the spectrum, however, one must not forget that in fact each term in
the Fourier Series expansion could be made up of both sine and cosine terms at any given
frequency and hence both magnitude and phase
are required for a complete representation of the time domain signal.
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