Update cheatsheet.fr.md

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

@@ -93,8 +93,8 @@ $`\overrightarrow{grad}\,f=\left(
 
       donc :
 
-$`\overrightarrow{grad}\big(div\,\overrightarray{U}\big)`$
-$`\quad = 
+$`\overrightarrow{grad}\big(div\,\overrightarrow{U}\big)`$
+$`\quad = \left(
 \begin{array}{l}
 \dfrac{\partial}{\partial x}\left( \color{blue}{\dfrac{\partial U_x}{\partial x}} \right)\\
 \dfrac{\partial}{\partial y}\left( \color{blue}{\dfrac{\partial U_y}{\partial y}} \right)\\