Question: what is the gradient of f(x y)?
Answer: The gradient of a function, f(x, y), in two dimensions is defined as: gradf(x, y) = Vf(x, y) = ∂f ∂x i + ∂f ∂y j . The gradient of a function is a vector field. It is obtained by applying the vector operator V to the scalar function f(x, y).