plot_polar(
    exp(sin(theta)) - 2 * cos(4 * theta), (theta, 0, 2 * pi),
    polar_axis=True)
# Expected:
## Plot object containing:
## [0]: parametric cartesian line: ((exp(sin(theta)) - 2*cos(4*theta))*cos(theta), (exp(sin(theta)) - 2*cos(4*theta))*sin(theta)) for theta over (0.0, 6.283185307179586)