I am going to go over signal form in the time and frequency domain. Please look at the figure. The left signal is represented in the time domain. The signal has only a DC component. The right signal is corresponding to the left one, and is represented in the frequency domain. The DC component in the time domain is represented as 0Hz in the frequency domain. Please click the “next” button at the bottom. The sine wave has a single frequency of 8Hz, and is shown in the right figure. Please click the “next” button at the bottom. This is a similar situation to the previous figure. The sine wave has a single frequency of 16Hz, and is shown in the right figure.