Update cheatsheet.fr.md

12.temporary_ins/69.waves/30.n3/20.overview/cheatsheet.fr.md

@@ -1404,10 +1404,10 @@ $`\quad\;\, = (A_{moy}+ \Delta A_{1-2})\,cos\,\theta_1 + (A_{moy} - \Delta A_{1-
 $`\begin{align}\quad\;\,= \big[ (\omega_{moy}&+ \Delta \omega_{1-2})\, t + \big(\overrightarrow{k}_{moy}+ \Delta \overrightarrow{k}_{1-2}\big)\cdot\overrightarrow{r}\\
 &+( \varphi_{moy} + \Delta \varphi_{1-2})\big]\end{align}`$
 
-$`\begin{align}\quad\;\,= \big[ \big(\underbrace{
-\omega_{moy} t &+ \overrightarrow{k}_{moy}\cdot\overrightarrow{r}+ \varphi_{moy}
+$`\begin{align}\quad\;\,&= \big[ \big(\underbrace{
+\omega_{moy} t + \overrightarrow{k}_{moy}\cdot\overrightarrow{r}+ \varphi_{moy}
   }_{\color{blue}{\theta_{moy}}  \big) \\
-& + \big(\underbrace{
+& \quad + \big(\underbrace{
   \Delta \omega_{1-2} t + \Delta \overrightarrow{k}_{1-2}\cdot\overrightarrow{r}+\Delta\varphi_{1-2}
   }_{
   \color{blue}{\theta_{1-2}