Update cheatsheet.fr.md

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

@@ -68,10 +68,12 @@ PRINCIPALES COMBINAISONS
    * <details markdown=1>
       <summary>Expressions en coordonnées cylindriques et sphériques</summary>
       * coordonnées cylindriques $`(\rho\,,\,\varphi\,,\,z)`$ :   
+        <br>
        $`\Delta\,\phi=\dfrac{1}{\rho}\dfrac{\partial}{\partial \rho}\left(\rho\,\dfrac{\partial \phi}{\partial \rho}\right)
         +\dfrac{1}{\rho^2}\dfrac{\partial^2 \phi}{\partial \varphi^2}+\dfrac{\partial^2 \phi}{\partial z^2}`$
       * coordonnées sphérique $`(r\,,\,\theta\,,\,\varphi)`$ :   
-       $`\Delta\,\phi=\dfrac{1}{r}\dfrac{\partial^2}{\partial r^2}(r\phi}
+        <br>
+       $`\Delta\,\phi=\dfrac{1}{r}\dfrac{\partial^2}{\partial r^2}(r\phi)
          + \dfrac{1}{r^2\,\sin\theta}\dfrac{\partial}{\partial \theta}\left(\sin\theta\dfrac{\partial \phi}{\partial \theta}\right)
          + \dfrac{1}{r^2\,\sin^2\theta}\dfrac{\partial^2 \phi}{\partial \varphi^2}`$
 
@@ -108,6 +110,7 @@ PRINCIPALES COMBINAISONS
    * <details markdown=1>
       <summary>Expressions en coordonnées cylindriques et sphériques</summary>
       * dans la base cylindrique unitaire $`(\vec{e_{\rho}}\,,\,\vec{e_{\phi}}\,,\,\vec{e_z})`$ :   
+        <br>
        $`\Delta\,\overrightarrow{U}=\left(\begin{array}{l}
          \dfrac{\partial^2 U_x}{\partial x^2}+\dfrac{\partial^2 U_x}{\partial x^2}+\dfrac{\partial^2 U_x}{\partial x^2}\\
          \dfrac{\partial^2 U_y}{\partial x^2}+\dfrac{\partial^2 U_y}{\partial x^2}+\dfrac{\partial^2 U_y}{\partial x^2}\\