I have a probably dumb question with the finite element method. Consider a 2D Poisson equation: $\nabla (a(x)\nabla u(x)) = f(x)$ with suitable boundary conditions. Suppose we solve the problem with finite element. In my problem, I am particular interested in the gradient $\nabla u$. I am wondering if there is some easier way to find the gradient. Can it by some by product of the finite element method for solving the equation?
Thanks in advance!