ClearAll[af]
af[u_] = (3 + 4 Cos[u] + Cos[ 2 u])/8 ;

Manipulate[
PolarPlot[ af[kd Cos[t] +u0],
{t, 0, Pi},
PolarAxesOrigin->{0,1 },
PolarGridLines->Automatic,PolarAxes->True,PolarTicks->{Table[{N[Pi/6 i],ToString[30 i]<>"°"},{i,-5,6}],Automatic}
]
,{{kd, 5 Pi/4, "k d"}, Pi/8, 2 Pi, Appearance -> "Labeled"}
,{{u0, 0, "(Subscript[u, 0])"}, 0, 2 Pi, Appearance -> "Labeled"}
, SaveDefinitions->True
]