ベクトル値函数：デカルトの正葉線
Author: knxm

t = 0.9 (slider from -5 to 5, step 0.1)
a = 1 (slider from -5 to 5, step 0.1)
h = 0.01 (slider from 0.01 to 2, step 0.01)
f(x) = 3 * a * x / (1 + x^(3))
g(x) = 3 * a * x^(2) / (1 + x^(3))
A: (f(t), g(t))
B: (f(t + h), g(t + h))
O = Intersect(xAxis, yAxis)
u = Vector(O, A)
v = Vector(O, B)
w = Vector(A, B)
C: A + w / h
z = Vector(A, C)
b: x^(3) + y^(3) - 3 * a * x * y = 0