d = CurveCartesian(((2 * cos((2 * φ))); φ), φ, 0, (2 * π))
b = CurveCartesian((1 + cos(φ); φ), φ, 0, (2 * π))
c = CurveCartesian((ℯ^(φ); φ), φ, 0, (2 * π))
a = CurveCartesian(((2 * φ); φ), φ, 0, (4 * π))