c = 2 (slider from 0 to 10, step 0.1)
F_1: (c, 0)
F_2: (-c, 0)
λ = 0.2 (slider from 0 to c, step 0.1)
lista1 = Sequence((x - c)^(2) + y^(2) = (i * λ)^(2), i, 1, 30)
lista2 = Sequence((x + c)^(2) + y^(2) = (i * λ)^(2), i, 1, 30)