fft,displacement, frequency

Hi; I can see the maximum displacement with Figure 1 which is Displacement-time grapf.

When I apply fft I can see the correct frequency but maximum displacement doesn't match with displacement .

I guess I made mistake when I applied FFT. Can you check and help?

    t=0:0.01:10;
t_step=0.01;
ts=1/t_step;
x=sin(1.66*t);

figure(1);
plot(t,x);

x =x' .*hann(length(x))*2;

N1=2^nextpow2(length(x));               
freq1=(0:1:(N1-1)/2)*ts/N1;             
fx1=fft(x,N1)/N1*2;                           
ffx1=abs(fx1(1:floor(N1/2))); 


figure(2);
plot(freq1,ffx1);