f(x,y)=\frac{xy^3}{x^2+y^2}

f(x, y) = If[x > -1 ∧ x < 1 ∧ y > -1.1 ∧ y < 1, (x * y^(3) / (x^(2) + y^(2))) + 0.5]
fx = Derivative(f(x, y), x)
fy = Derivative(f(x, y), y)
A = Point(xAxis)
B: (x(A), y(A), f(x(A), y(A)))
C = Point(yAxis)
D: (x(C), y(C), f(x(C), y(C)))
g = Segment(D, D + (0.4, 0, 0))
h = Segment(D + (0.4 * (1, 0, fx(x(C), y(C)))), D + (0.4 * (1, 0, 0)))
v = If(y(C) ≟ 0, Vector[(0, 0, 0.5), (0.4, 0, 0.5)], Vector[D, D + (0.4 * (1, 0, fx(x(C), y(C))))])
u = If(x(A) ≟ 0, Vector[(0, 0, 0.5), (0, 0.4, 0.5)], Vector[B, B + (0.4 * (0, 1, fy(x(A), y(A))))])
F = (-2.444, 4.844)
G = (-0.744, 4.844)