A = Point(xAxis)
B = Point(yAxis)
a: x(A)
b: y(B)
f(x, y) = x^(2) + y^(2)
c = OrthogonalPlane(A, xAxis3D)
d = OrthogonalPlane(B, yAxis3D)
P: (a, b, f(a, b))
f_x = Derivative(f(x, y), x)
f_y = Derivative(f(x, y), y)
r_x = Vector(P, P + (1, 0, f_x(a, b)))
r_y = Vector(P, P + (0, 1, f_y(a, b)))
n = Vector(P, P + (-f_x(a, b), -f_y(a, b), 1))
e: -f_x(a, b) * (x - a) - f_y(a, b) * (y - b) + z - f(a, b) = 0