more about polar_plot here

polar_plot

polar_plot(4*cos(3*x),(x, 0, 2*pi))

polar_plot(cos(1.65*x) + (1/4)*cos(5*x), (x, 0, 2*pi), color="green", thickness=5, axes = False)

polar_plot(sin(1.65*(pi/2 - x)) + (1/4)*sin(5*(pi/2 - x)), (x, -3*pi/2, pi/2), color="green", thickness=5, axes = False)