Variable rise and decayYou can probably guess that sawtooth waves can have rise and decay slopes in an infinitenumber of different combinations. One example is shown in Fig. 9-5. In this case, thepositive-going slope is the same as the negative-going slope. This is a triangular wave.Complex and irregular waveforms1699-4Slow-rise, fast-decay sawtooth, also called a ramp.9-5Triangular wave.Complex and irregular waveformsThe shape of an ac wave can get exceedingly complicated, but as long as it has a defi-nite period, and as long as the polarity keeps switching back and forth between positiveand negative, it is ac.Fig. 9-6 shows an example of a complex ac wave. You can see that there is a period,and therefore a definable frequency. The period is the time between two points on suc-ceeding wave repetitions.With some waves, it can be difficult or almost impossible to tell the period. This isbecause the wave has two or more components that are nearly the same magnitude.When this happens, the frequency spectrum of the wave will be multifaceted. The en-ergy is split up among two or more frequencies.