Update cheatsheet.fr.md

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

@@ -1404,8 +1404,15 @@ $`\quad\;\, = (A_{moy}+ \Delta A_{1-2})\,cos\,\theta_1 + (A_{moy} - \Delta A_{1-
 $`\begin{align}\quad\;\,= \big[ (\omega_{moy}&+ \Delta \omega_{1-2})\, t + \big(\overrightarrow{k}_{moy}+ \Delta \overrightarrow{k}_{1-2}\big)\cdot\overrightarrow{r}\\
 &+( \varphi_{moy} + \Delta \varphi_{1-2})\big]\end{align}`$
 
-$`\begin{align}\quad\;\,= \big[ \big(\underbrace{\omega_{moy} t &+ \overrightarrow{k}_{moy}\cdot\overrightarrow{r}+ \varphi_{moy}}_{\color{blue}{\theta_{moy}}\big) \\
-&+ \big((\underbrace{\Delta \omega_{1-2} t + \Delta \overrightarrow{k}_{1-2}\cdot\overrightarrow{r}+\Delta\varphi_{1-2}}_{\color{blue}{\theta_{1-2}}\big)\big]\end{align}`$
+$`\begin{align}\quad\;\,= \big[ \big(\underbrace{
+\omega_{moy} t &+ \overrightarrow{k}_{moy}\cdot\overrightarrow{r}+ \varphi_{moy}
+  }_{\color{blue}{\theta_{moy}}  \big) \\
+& + \big(\underbrace{
+  \Delta \omega_{1-2} t + \Delta \overrightarrow{k}_{1-2}\cdot\overrightarrow{r}+\Delta\varphi_{1-2}
+  }_{
+  \color{blue}{\theta_{1-2}
+  }
+  \big)\big]\end{align}`$