Trying to get magnitude of freq domain

Hi im new to matlab and im trying to figure out what i am doing wrong or how to do this correctly. - find and sketch the time-domain waveform and frequency-domain magnitude spectrum of the bandpass signal x(t)=sinc(100t) cos(400t).

heres what i have :

w1=100; w2=400*pi; t=[0:.001:.05]; x= sinc(w1*t).*cos(w2*t); %plot(t,x) wmin = -20; wmax = 20; w = {wmin,wmax,}; ffplot(x,w)

Answer 1

[Image Analyst]

How about this:

workspace;  % Make sure the workspace panel is showing.
fontSize = 20;
format compact;

w1=100;
w2=400*pi;
t=[0:.0001:.05];
x= sinc(w1*t).*cos(w2*t);
subplot(2,1,1);
plot(t, x, 'b-');
grid on;
title('The Time Domain Signal', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
theSpectrum = fft(x);
subplot(2,1,2);
plot(fftshift(real(theSpectrum)));
grid on;
title('The Real Part of the Spectrum', 'FontSize', fontSize);

Answer 2

[Youssef Khmou]

hi, Aaron,

The response that "ImageAnalyst" gave is correct but it shows wrong frequencies,

Here is the code to produce the two figures :

   w1=100; 
   w2=400*pi; 
   t=[0:.001:.05]; 
   x= sinc(w1*t).*cos(w2*t);
   figure, plot(t,x) , title (' Time Domain'),
   Fs=1/.001 %  From your time axis but also it must satisfy the  Nyquist            %condition which is  Fs > 2* max(F) your max frquency is F=200 Hz 

   L=length(x);
   N=ceil(log2(L));
   fx=fft(x,2^N)/(L/2);% when you use 2^N the finit ft becomes fast .
   Power=fx.*conj(fx);
   f=(Fs/2^N)*(0:2^(N-1)-1);
   figure,
   plot(f,sqrt(Power(1:2^(N-1))),'r'),
   xlabel('  Frequency (Hz)'),
   ylabel('|F(Y)|'),
   title('  Amplitude Spectrum'), grid on;