Including VectorField components in an equation in problem.add_equation("...")

[aratava]

Is there a way to include vector components when defining an equation through the problem.add_equation("...")? say for example dx(dx(A_x))+dy(A_y)+lift(tau)=0, where A_x and A_y are supposed to be x and y components of VectorField A. How to access vector components in this syntax?