Update cheatsheet.fr.md

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

@@ -131,6 +131,16 @@ visible: false
     \end{array}
    \right)`$**
 
+  **$`\overrightarrow{\Delta}=
+   \left(
+   \begin{array}{l}
+    \dfrac{\partial^2 U_x}{\partial x^2} + \dfrac{\partial^2 U_x}{\partial y^2} + \dfrac{\partial^2 U_x}{\partial z^2}
+    \end{array}
+   \right)`$**
+   
+     **$`\overrightarrow{\Delta}=\dfrac{\partial^2 U_x}{\partial x^2} + \dfrac{\partial^2 U_x}{\partial y^2} + \dfrac{\partial^2 U_x}{\partial z^2}`$**
+
+
 <br>
 
 ##### 2 - Champ vectoriel et opérateurs $`div`$ et $`\overrightarrow{rot}`$