I hope this is the right Place for my Question
Why it doesn't this work?
f[a_, r_, t_, v_, \[Omega]_] :=
v t (1 + (1/(1 - (r/a) Cos[\[Omega]*t])))
g[a_, r_, t_,
v_, \[Omega]_] := (r Sin[\[Omega] t])/(1 - (r/a) Cos[\[Omega] t])
Manipulate[
ParametricPlot[{f[a, r, t, v, \[Omega]],
g[a, r, t, v, \[Omega]]}, {t, 0, 10}], {r, 0, 1}, {a, 1, 20}, {v,
0, 20}, {\[Omega], 0, 2 \[Pi]}]