Objective: 

To show how to calculate rms voltages (and currents) for various
periodic waveforms.

Steps: 

Observe some examples of waveforms you may encounter that have
an average value of zero. 

Examine the power dissipated in a resistor supplied by an ideal
squarewave. 

Find the rms of a triangular waveform. 

The rms value of a sine wave is very important in AC circuit analysis. 

Recall how to calculate rms and how it is useful in circuits supplied
by a periodic waveform. 