This is the original code:
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)
It outputs:
This code is wrong because the sampling frequency, Ts, is to large to produce an accurate recreation of the signal. I fixed this bug by reducing the sampling time by a factor of 20.
F0 = 13; T0 = 1/F0; Ts = .05*T0; t = 0:Ts:13*T0; x = real(exp(j*(2*pi*F0*t-pi/2))); plot(t,x)
Now the output looks like this: