Update cheatsheet.fr.md

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

@@ -117,22 +117,18 @@ visible: false
     \;\left(\dfrac{\partial^2 U_z}{\partial x^2}+\dfrac{\partial^2 U_z}{\partial y^2}+\dfrac{\partial^2 U_z}{\partial z^2}\right)-\dfrac{1}{\mathscr{v}^2}\dfrac{\partial^2 U_z}{\partial t^2}=0   
     \end{array}\right.`$*   
     <br>
-    **Chacune des composantes du champ vérifie l'équation d'onde scalaire**.
+    *Chacune des composantes du champ vérifie l'équation d'onde scalaire*.
 
 * L'expression du laplacien vectoriel **$`\overrightarrow{\Delta}\,\overrightarrow{U}`$**
   d'un vecteur $`\overrightarrow{U}`$ **en coordonnées cartésiennes** est :   
   <br>
-  **$`\overrightarrow{\Delta}=
-   \left(
-   \begin{array}{l}
+  **$`\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}\\
     \dfrac{\partial^2 U_y}{\partial x^2} + \dfrac{\partial^2 U_y}{\partial y^2} + \dfrac{\partial^2 U_y}{\partial z^2}\\    
     \dfrac{\partial^2 U_z}{\partial x^2} + \dfrac{\partial^2 U_z}{\partial y^2} + \dfrac{\partial^2 U_z}{\partial z^2   
-    \end{array}
-   \right)`$**
+    \end{array}\right)`$**
 
-  **$`\overrightarrow{\Delta}=
-   \begin{pmatrix}
+  **$`\overrightarrow{\Delta}=\begin{pmatrix}
     \dfrac{\partial^2 U_x}{\partial x^2} + \dfrac{\partial^2 U_x}{\partial y^2} + \dfrac{\partial^2 U_x}{\partial z^2}\\
     \dfrac{\partial^2 U_y}{\partial x^2} + \dfrac{\partial^2 U_y}{\partial y^2} + \dfrac{\partial^2 U_y}{\partial z^2}\\    
     \dfrac{\partial^2 U_z}{\partial x^2} + \dfrac{\partial^2 U_z}{\partial y^2} + \dfrac{\partial^2 U_z}{\partial z^2