The previous page showed the Time Domain and Frequency Domain graphs for a COSINE waveform.

This page shows the responses for a SINE wave.

You will notice that the frequency response is identical to that of the cosine wave for a particular frequency. There is not enough information to determine whether a sine or cosine (or delayed/advanced cosine) produced the response.

For some purposes the information shown is adequate (e.g. using the sum of sine waves to produce a non-sinusoidal signal). But for many purposes we need the missing information. This will be discussed on the next page.