lta_{ij}.$$</p>
<p>But it is diffcult to find the "orthogonal" dual basis for $\chi_1,\chi_2$. One choice is $$l_f^1(u) := \int_{T} u\cdot n_{ik}\, dx, \quad l_f^2(u) := \int_{T} u\cdot n_{ij}\, dx.$$ Then $l_f(\phi) \neq 0, l_f(\psi) \neq 0$. The good news is $d_e^{\phi}(\chi) = d_e^{\psi}(\chi) = 0$ as $\lambda_k\phi _{ij}\cdot n_e = 0$ either $\lambda_k|e = 0$ or $\phi_{ij}\cdot n_e = 0$.</p>
<p>We need to solve a small system to get the coefficients for bases $\chi$. Fortunately this has been done in qu