Using the DFT

sampling $sin(2*pi*t)$ and taking the DFT we get this graph:

Script for matlab:

clear all;
t=0:.01:1;
T=0.20;
ts=0:T:1;
f1=2;
f2=1/0.125;
x = sin(2*pi*3*t); %this is the function
plot(t,x); % plot the original signal
X = fft(x); % take the DFT
pause (2);
plot (t,X); %plot the DFT of the signal