Update cheatsheet.fr.md

12.temporary_ins/69.waves/20.n2/20.overview/cheatsheet.fr.md

@@ -1251,16 +1251,17 @@ et propagation des zéros](https://m3p2.com/fr/temporary_ins/waves/n3/overview/2
       \boldsymbol{\mathbf{ U(x,t) = A\cdot & cos\big(\alpha_{moyen} - \dfrac{\Delta\varphi}{2}\big)}}\\
       & \boldsymbol{\mathbf{ + A\cdot cos\big(\alpha_{moyen} + \dfrac{\Delta\varphi}{2}\big)}}
       \end{align}`$** 
-
-  **$`\begin{align}{\mathbf{
-      U(x,t) = A\cdot & cos\big(\alpha_{moyen} - \dfrac{\Delta\varphi}{2}\big)\\
+      
+  **$`\begin{align}\boldsymbol{\mathbf{
+       U(x,t) = A\cdot & cos\big(\alpha_{moyen} - \dfrac{\Delta\varphi}{2}\big)\\
       & + A\cdot cos\big(\alpha_{moyen} + \dfrac{\Delta\varphi}{2}\big)
-      }\end{align}`$** 
+      }}\end{align}`$** 
       
-  **$`\begin{align}{
-      U(x,t) = A\cdot & cos\left(\alpha_{moyen} - \dfrac{\Delta\varphi}{2}\right)\\
-      & + A\cdot cos\left(\alpha_{moyen} + \dfrac{\Delta\varphi}{2}\right)
-      \end{align}`$** 
+  **$`\boldsymbol{\mathbf{\begin{align}
+       U(x,t) = A\cdot & cos\big(\alpha_{moyen} - \dfrac{\Delta\varphi}{2}\big)\\
+      & \boldsymbol{\mathbf{ + A\cdot cos\big(\alpha_{moyen} + \dfrac{\Delta\varphi}{2}\big)
+     \end{align}}}`$** 
+
       
       à continuer