FFT returns a different amplitude value, why?

Dear Colleagues,

I am working in this code (attached):

t = 0:0.05:4*pi; x=2+1.5*cos((2*pi/360)*60*t+(2*p)i/360)*90) N1=length(t) n1=log2(N1) n1=ceil(n1) vet = 2^n1 %multiple of 2^n;

b = N1+1; while b~=vet+1 t(b)= (t(b-1)-t(b-2))+t(b-1) %complementing the time vector to the lentgh vet; x(b)= 0 %comlementing the vector x with zeros until lenght vet; b=b+1 end

sample_rate=1/(abs(t(2)-t(1))) f=sample_rate*((0:vet/2))/vet %vector frequency associated; n=length(f) X=fft(x) fftX=X*1/(vet) abs_fftX=abs(fftX(1:n)) figure(1) stem(f,abs_fftX)

When I compute fft and plot (stem) the result, appears 1.94 in the graphic origin (phase is zero) instead of 2. It needs to be 2 (phase is zero), because it is a DC signal from x= 2 +1.5*cos((2*pi/360)*60*t+(2*p)i/360)*90). So, maybe in the others frequencies could be wrong too. Could somebody teach me how to fix it? Thanks a lot.