Field and equipotentials for

 f(x,y)=x^2+y^2

ds = 0.14 (slider from 0 to 0.5, step 0.01)
Y_1 = 0.42 (slider from -20 to 20, step 0.01)
X_1 = 0.73 (slider from -10 to 10, step 0.01)
f(x, y) = x^(2) + y^(2)
k = Derivative(f, y, 1)
a = Derivative(f, x, 1)
A: (X_1, Y_1)
gradf = Vector((X_1, Y_1), (X_1 + a(X_1, Y_1), Y_1 + k(X_1, Y_1)))
L = Sequence(f(x, y) = a, a, 0, 4)