# Amplitude Spectrum of a function

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aliza mustafa on 18 Sep 2022
Answered: Chunru on 19 Sep 2022
Hi,
My question is related to plotting amplitude spectrum.
Problem 1: (I have solved it) I have to represent the following function as a discrete set of N=100 numbers separated by time increment of 1/N:
e(t) = 3sin2.1t + 2sin1.9t
I did it using stem function and plotted it.
Problem 2: (I have question about it) The next thing was to repeat the same above all, using dataset of 200 points with time increment of 1/N and 1/2N.
My question is a bit basic but I just want to clear if I am following the right path to solve my problem.
I want to ask that for problem 2, for both 1/N and 1/2N, should I use N=200 (as I believe it is separate problem)?
A few of my mates has suggsted to use N=100 for 1/N and N=200 for 1/2N.
which one is right thing?
Any help will be highly appreciated. Thanks
dpb on 18 Sep 2022
We can't answer that as posed; it is totally dependent upon how the question itself was written; a paraphrase of what it says isn't the same thing...it may well have been ambiguous as written; would seem the logical thing to do would to get the instructor to clarify (or just solve the problem with both interpretations and explain why).

Chunru on 19 Sep 2022
If you are studying the effect of sampling frequency, you may want to fix the signal duration, for example .
In this case, you have:
• fs = N; t = 0:1/fs:1; which equivelant to t=0:1/N:1, (whether N=100 or 200)