Equation 18.28.280B2DE1BB9170

\begin{equation} \frac{\mathrm{d}}{\mathrm{d}t}\mathcal{E}_{\theta ,K}^{\varphi }(v+tf) = \int _ K f\, \theta ^ n_{P_{\theta ,K}[\varphi ]_{\mathcal{I}}(v+tf)} \end{equation}