Please refer to the attachment...

Thanks...

i) Peak to peak time is the time interval between two successive peaks.

To do this, drop a vertical line from the first peak to the time axis below, and drop another vertical from the second peak to the time axis below. Then, subtract the smaller time from the larger time you read.

Another more accurate method is to find the time interval between many peaks and then divide by the number of peaks.

ii) The time that you got is called the periodic time, it's basically the time for the signal to undergo a complete cycle. The frequency is the inverse of periodic time, and can be expressed by the following equation:



f is frequency, T is the periodic time.

iii) Unfortunately, I don't know how to do this part :(

The FFT plot will be empty except for a single delta function (usually drawn as an arrow pointing straight up) at the frequency f that you calculated in part ii. That's because there's only a single frequency component to the original time-domain signal. If it was a more complex signal, there would be more frequency-domain content in the FFT.

Actually, I should further qualify my answer. Technically, there's also a second delta function at frequency -f. That's often ignored, since frequency is usually plotted for positive values only, but the FFT algorithm will indeed return that delta function as well.