sloution for my question

we want to sample the signal { X(t)=sin(2 ft) } at frecuncy =100 , for f consider the following the three different values , f=20 , 80 ,120 ,take the sampled signal and drow the plot of fourier transform.

Answer 1

[Bhaskar R]

f = [20, 80, 120];    % your frequencies
fs = 100;    % sampling frequency
t = 0:1/fs:1-1/fs;    % time
A = 1;     % amplitude here assumed as 1
for ii = 1:length(f)
    figure(ii)
    X = A*sin(2*pi*f(ii)*t);
    ft = abs(fft(X));
    subplot(211), plot(t, X), title(['Signal of frequency: ', num2str(f(ii))]);grid on
    subplot(212), plot(ft), title(['FFT of Signal : ', num2str(f(ii))]);grid on
end
% note: not tested