T=100;
dT=1/50;
t=[-T:dT:T];
x=2*sin(2*pi*0.05*t);
subplot(211);
plot(t,x);
F=5;
dF=0.01;
f=[-F:dF:F];
i=1;
for fv=f
	X(i)=x*exp(-j*2*pi*fv*t')*dT;
	i=i+1;
end
subplot(212);
plot(f,abs(X));