Update cheatsheet.fr.md

12.temporary_ins/90.electromagnetism-in-vacuum/10.maxwell-equations/20.overview/cheatsheet.fr.md

@@ -19,7 +19,7 @@ lessons:
 <!--caligraphie de l'intégrale double curviligne-->
 $`\def\dens{\large{\varrho}\normalsize}`$
 $`\def\oiint{\displaystyle\mathop{{\iint}\mkern-18mu \scriptsize \bigcirc}}`$
-$`\def\soiint\normalsize{\mathop{{\iint}\mkern-18mu \scriptsize \bigcirc}}`$
+$`\def\soiint{\mathop{{\iint}\mkern-18mu \scriptsize \bigcirc}}`$
 $`\def\Ltau{\large{\tau}\normalsize}`$
 $`\def\Sopen{\mathscr{S}_{\smile}}`$
 $`\def\Sclosed{\mathscr{S}_{\displaystyle\tiny\bigcirc}}`$
@@ -121,6 +121,15 @@ $`\Longrightarrow`$
 **$`\mathbf{\displaystyle \quad\oiint_{S\leftrightarrow\Ltau} \overrightarrow{E}\cdot\overrightarrow{dS}
 = \dfrac{1}{\epsilon_0} \cdot \iiint_{\Ltau} \rho \cdot d\tau = \dfrac{Q_{int}}{\epsilon_0}}`$**
 
+   * $`\left.\begin{array}{l}
+\displaystyle\iiint_{\Ltau} div \overrightarrow{E}\,d\tau = \iiint_{\Ltau}\dfrac{\dens}{\epsilon_0}\,d\tau \\
+\displaystyle\iiint_{\Ltau} div\;\overrightarrow{E} \cdot d\tau = \displaystyle 
+\oiint_{S\leftrightarrow\Ltau} \overrightarrow{E}\cdot\overrightarrow{dS}
+\end{array}\right\}`$
+$`\Longrightarrow`$
+**$`\mathbf{\displaystyle \quad\oiint_{S\leftrightarrow\Ltau} \overrightarrow{E}\cdot\overrightarrow{dS}
+= \dfrac{1}{\epsilon_0} \cdot \iiint_{\Ltau} \rho \cdot d\tau = \dfrac{Q_{int}}{\epsilon_0}}`$**
+
 
 * *Maxwell-flux* :