Update cheatsheet.fr.md

12.temporary_ins/90.electromagnetism-in-vacuum/20.electromagnetic-waves-vacuum/20.overview/cheatsheet.fr.md

@@ -192,8 +192,9 @@ figure à faire.
     &\dfrac{\partial E_x}{\partial z}-\dfrac{\partial E_z}{\partial x}=-\dfrac{\partial B_y}{\partial t}\\
     &\dfrac{\partial E_y}{\partial x}-\dfrac{\partial E_x}{\partial y}=-\dfrac{\partial B_z}{\partial t}\\
     \\
-    &\dfrac{\partial E_z}{\partial y}=\dfrac{\partial E_y}{\partial z}=\dfrac{\partial E_x}{\partial z}=\dfrac{\partial E_z}{\partial x}\\
-    &\quad =\dfrac{\partial E_y}{\partial x}=\dfrac{\partial E_x}{\partial y}=0
+    &\dfrac{\partial E_x}{\partial x}=\dfrac{\partial E_y}{\partial x}=\dfrac{\partial E_z}{\partial x}
+    =\dfrac{\partial E_x}{\partial y}\\
+    &\quad =\dfrac{\partial E_y}{\partial y}=\dfrac{\partial E_z}{\partial y}=0
     \end{align}\right\}`$   
     <br>
     *$`\Longrightarrow\left\{