Figure 2.16. There are three parts to this figure. The first part shows one cycle of a sine wave. On the same axis is another sine wave showing 3 cycles and 1 third the amplitude. A heavy line represents the point by point sum of the two waves. It starts at zero, goes up more quickly than either of the other two waves, reaches a peak which is about the same height as the one cycle wave, drops a little, goes back up to the same height and descends to zero. It keeps going down below zero then back up a little back down then back up to zero. The negative part looks the same as the positive part but mirror imaged. In the second part the sum wave from the first part is drawn along with 5 cycles of a sine wave which has an amplitude of 1 fifth of the original one cycle sine wave. The sum goes up to about the same height as before, down a little, up, down, up, each of the ups and downs are equal in height, down to zero and on below, up, down, up, down, and up to zero. The third part has the sum from the second part along with 7 cycles of a sine wave which has an amplitude of 1 seventh of the original. The sum wave goes up to a peak, then down, up, down, up, down, up, each of the ups and downs are equal in height, then down to and through zero to go down, up, down, up, down, up down, then back up to zero. End verbal description.
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