  We propose the application of graphical convolution to the analysis of the
resonance phenomenon. This time-domain approach encompasses both the finally
attained periodic oscillations and the initial transient period. It also
provides interesting discussion concerning the analysis of non-sinusoidal
waves, based not on frequency analysis, but on direct consideration of
waveforms, and thus presenting an introduction to Fourier series. Further
developing the point of view of graphical convolution, we come to a new
definition of resonance in terms of time domain.
