Galerkin orthogonality

If $u$ solves a variational problem and $u_h$ is its conforming Galerkin method approximation in $V_h$, thenfor every $v_h\in V_h$.

For a continuous coercive bilinear form with continuity constant $M$ and coercivity constant $\alpha$, a conforming finite-element solution satisfiesFor a symmetric problem measured in its energy norm, the constant is one.