Céa lemma
= Céa lemma
{c}
{wiki=Céa's_lemma}
For a continuous coercive bilinear form with continuity constant $M$ and coercivity constant $\alpha$, a conforming finite-element solution satisfies
$$
\|u-u_h\|_V\leq\frac M\alpha
\inf_{v_h\in V_h}\|u-v_h\|_V.
$$
For a symmetric problem measured in its <energy norm>, the constant is one.