I am trying to plot a phase angle vs. frequency curve numerically for the steady state condition of the following equation
x''[t] + 2*\[Zeta]*2 ζ x'[t] + x[t] == Cos[w*t]Cos[w t]
where w
is the forcing frequency, and the initial conditions are x[0] == 0, x'[0] == 0
. A similar plot is shown here. :