Update cheatsheet.fr.md

12.temporary_ins/08.grad-div-rot/70.combinaisons-of-operators/20.overview/cheatsheet.fr.md

@@ -92,10 +92,23 @@ $`\overrightarrow{grad}\,f=\left(
 
       donc :
 
-$`\overrightarrow{grad}\big(div\,\overrightarrow{U}\big)`$
+$`\overrightarrow{grad}\big(\color{blue}{div\,\overrightarrow{U}}\big)`$
 $`\quad = \left(
 \begin{array}{l}
 \dfrac{\partial}{\partial x}\left( \color{blue}{\dfrac{\partial U_x}{\partial x}+\dfrac{\partial U_y}{\partial y}+\dfrac{\partial U_z}{\partial z}} \right)\\
 \dfrac{\partial}{\partial y}\left( \color{blue}{\dfrac{\partial U_x}{\partial x}+\dfrac{\partial U_y}{\partial y}+\dfrac{\partial U_z}{\partial z}} \right)\\
 \dfrac{\partial}{\partial z}\left( \color{blue}{\dfrac{\partial U_x}{\partial x}+\dfrac{\partial U_y}{\partial y}+\dfrac{\partial U_z}{\partial z}} \right)
 \end{array}\right)`$
+
+      et nous obtenons :
+
+$`\overrightarrow{grad}\big(div\,\overrightarrow{U}\big)`$
+$`\quad = \left(
+\begin{array}{l}
+\dfrac{\partial^2 U_x}{\partial x^2}+\partial^2 U_y}{\partial x \partial y}+\partial^2 U_z}{\partial x \partial z}\\
+\dfrac{\partial^2 U_x}{\partial y \partial x}+\partial^2 U_y}{\partial y^2}+\partial^2 U_z}{\partial y \partial z}\\
+\dfrac{\partial^2 U_x}{\partial z \partial x}+\partial^2 U_y}{\partial z \partial y}+\partial^2 U_z}{\partial z^2}
+\end{array}\right)`$
+
+
+\end{array}\right)`$
\ No newline at end of file