f(x, y) = x^(2) + y^(2)
f_x = Derivative(f(x, y), x)
f_y = Derivative(f(x, y), y)
A = Point(xAxis)
B = Point(yAxis)
a: x(A)
b: y(B)
P: (a, b, f(a, b))
u = Vector((a, b, f(a, b)), (a + 1, b, f(a, b) + f_x(a, b)))
v = Vector((a, b, f(a, b)), (a, b + 1, f(a, b) + f_y(a, b)))
w = Vector(P, (a - f_x(a, b), b - f_y(a, b), f(a, b) + 1))
p = 0.2
list1 = Sequence(Segment[(t, b, f(t, b)), (t + p, b, f(t + p, b))], t, -4, 4, p)
list2 = Sequence(Segment[(a, t, f(a, t)), (a, t + p, f(a, t + p))], t, -4, 4, p)
c: -f_x(a, b) * (x - a) - f_y(a, b) * (y - b) + z - f(a, b) = 0