Q 8.4  p.208

gw = w^2/(s^2 + 2 z wn s + wn^2) /. s ->  I w /. 
            w ->  p wn /. z ->  0.1 /. 
        wn ->  1

oscillo[p_ , 
        ap_, ϕp_] := {pulse = 0.1 (Sign[Cos[ p t] - 0.99] + 1); 
        xt = ap Cos[ 
              p t + ϕp °]; 
Plot[{pulse, 
            xt}, {t, 0, 15}, PlotPoints ->  500, 
          PlotRange ->  {-1.5, 1.5}]}

gwp = 
        gw ϵ Exp[I θ ] /. {ϵ -> 
              1, θ ->  
              45  °};
zu1 = 
      Plot[Abs[gw /. z ->  0.1], {p, 0, 3}, 
        GridLines -> Automatic , PlotRange ->  {0, 5}]; {ap = 
        Abs[gwp /. p ->  0.75], ϕp = 
        Arg[gwp /. p ->  0.75]/Degree}

oscillo[0.75, ap, ϕp]

gwpt = 
        gw (ϵ Exp[I θ ] + ϵt  Exp[
                    I ( θt) ]) /. {ϵ -> 
              1, θ ->  45  °, ϵt -> 
              0.5, θt ->  -90 °};
zu2 = 
      Plot[Abs[gwpt], {p, 0, 3}, GridLines -> Automatic , 
        PlotRange ->  {0, 5}]; {apt = 
        Abs[gwpt /. p ->  0.75], ϕpt = 
        Arg[gwpt /. p ->  0.75]/Degree}

oscillo[0.75, apt, ϕpt]

gwpc = 
        gw (ϵ Exp[I θ ] + ϵt 2 Exp[
                    I ( θt - 
                          48  °) ]) /. {ϵ -> 
              1, θ ->  45  °, ϵt -> 
              0.5, θt ->  -90 °};
zu3 = 
      Plot[Abs[gwpc], {p, 0, 3}, GridLines -> Automatic , 
        PlotRange ->  {0, 5}]; {apc = 
        Abs[gwpc /. p ->  0.75], ϕpc = 
        Arg[gwpc /. p ->  0.75]/Degree}

oscillo[0.75, apc, ϕpc]

Show[zu1, zu2, zu3]