The original code below uses Ts of 0.07, or a sampling rate of 0.07 seconds. Therefore, the plot appears to only show one cycle of the sinusoid.
F0 =13; T0 =1/F0; Ts = 0.07; t = 0:Ts:13*T0; x = real(exp(j*(2*pi*F0*t-pi/2))); plot(t,x);
If the sampling rate is changed to 0.001, it will be enough to see all 13 cycles of the sinusoid. Increasing the sampling rate will give a much smoother representation of the sinusoid.
F0 =13; T0 =1/F0; Ts = 0.001; t = 0:Ts:13*T0; x = real(exp(j*(2*pi*F0*t-pi/2))); plot(t,x);