N=45;
n=0:N-1;
t=0.01*n;
f=2*pi*n/N;
xt=2*sin(4*pi*t)+5*cos(8*pi*t);
xk=fft(xt);
Axk=abs(xk);
subplot(3,1,1);
stem(f,Axk);
xlabel('k');
ylabel('X(k)');
title('the DFT of the Signal');