Update cheatsheet.fr.md

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

@@ -352,7 +352,7 @@ $`\forall \alpha \in \mathbb{R}\;,\,`$ **$`\large{exp{\,\alpha} = cos \,\alpha +
                &\quad\quad\text{avec }\mathbf{\color{blue}{\underline{A}=A\; e^{\,i\varphi} }}\\
                &\quad\quad\quad\color{blue}{\text{amplitude complexe}}\end{align}`$
 
-     3D : $`\begin{align}\color{brown}{\quad\underline{U}(x,t) &=A\cdot e^{\,i\,(\omega t - \vec{k}\cdot\vec{r} + \varphi)}  }\\
+     3D : $`\begin{align}\quad\underline{U}(x,t) &=A\cdot e^{\,i\,(\omega t - \vec{k}\cdot\vec{r} + \varphi)}\\
                &\text{toto}
                \end{align}`$