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greater. Triangular waves like Fig. 24.1cbut with equal up and down
slopes, on the contrary, are easier because the harmonic amplitudes
decline inversely as the square of the harmonic number.
The foregoing are just a few examples of the Fourier principle
(Sec.
19.6) which states that any periodic (i.e., exactly repeating)
waveform can be analysed into harmonic sine waves. Put in the
reverse way, any periodic waveform can be synthesised by adding
together sine waves, as we have been doing in Fig. 24.2 for the
particular case of square waves. Reference books on signals often
include formulae for the most useful waveforms. As with those w