b = 1.83 (slider from 0 to 2, step 0.01)
a = CurveCartesian(((-2 * b) * cos(t) / (cos(t)^(2) - 2)), (((2 * b) * sin(t)) * cos(t) / (cos(t)^(2) - 2)), t, 0, 6.28319)
c(x, y) = y^(2)  <  x^(2)