FESpacesWithLinearConstraints

[DaniStauber]

Hi There, i've been working in a Poisson tensorial problem. I was working on polar coordinates, so my variables (in components) are $T^{rr}$, $T^{r\theta}$, $T^{\theta \theta}$, and i found the boundary conditions necessary to make my problem well-possed. For $T^{rr}$ and $T^{r\theta}$ are Dirichlet conditions and for $T^{\theta \theta}$ a Robin condition. My problem is that the weak formulation must be in cartesian coordinations so i was looking for a tool that allow me to give Constrains between $T^{xx}$, $T^{xy}$ and $T^{yy}$ in the boundary. I though that maybe the FESpacesWithLinearConstraints could be that tool, but i dont really understand the example. My Constrain has coefficients that depends on the coordinates, because there are linked with a change of variables. Now im continue trying to understand the tool of FESpacesWithLinearConstraints, but any kind of help will be welcome.

[DaniStauber]

I want to use a tool in a tensor problem involving something like this kind:
$$\Delta \phi_1 = \rho_1$$
$$\Delta \phi_2 = \rho_2$$ on a circle with boundary conditions like
$$\phi_1 +f_1(x) \phi_2 =g_1(x)$$
$$\partial_r \phi_1 +f_2(x) \phi_2 =g_2(x)$$.

I would like to know if this tool is useful for problems of this type, or if there is another way to solve it.