a1(x, y) = x - y - ((x^(2) + y^(2)) * x)
a2(x, y) = x + y - ((x^(2) + y^(2)) * y)
a = CurveCartesian(cos(t), sin(t), t, 0, (2 * π))
t1 = Sequence(((2 * π) * k / 10), k, 0, 9)
C1: -0.99
r(x) = If[0 ≤ x ≤ 100, ℯ^(x) / sqrt(C1 + ℯ^((2 * x)))]
phi0: π / 4
b = CurveCartesian((r(t) * cos(t + phi0)), (r(t) * sin(t + phi0)), t, 0, 10)
r2(x) = ℯ^(x) / sqrt(1 + ℯ^((2 * x)))
c = CurveCartesian((r2(t) * cos(t + phi0)), (r2(t) * sin(t + phi0)), t, -1.5, 10)