Update cheatsheet.fr.md

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

@@ -57,10 +57,10 @@ $`\newcommand{\ddpt}[1]{\overset{\large\bullet\bullet}{#1}}`$
      $`U_1(x,t) = A\cdot cos(kx - \omega t + \varphi_1)`$.  
      $`U_2(x,t) = A\cdot cos(kx - \omega t + \varphi_2)`$.
 
-$`U(x,t) =A\;\big[cos(\underbrace{kx - \omega t}_{\text{  posons }\\ kx - \omega t \,=\, \alpha} + \varphi_1) + cos(\underbrace{kx - \omega t}_{=\; \alpha} + \varphi_1)\,\big]`$
 
 
-$`\begin{align} \mathbf{\color{'brown'}{U(&x,t)}} = U_1(x,t) + U_2(x,t) \\
+
+$`\begin{align} \mathbf{\color{brown}{U(&x,t)}} = U_1(x,t) + U_2(x,t) \\
 &\\
 &=A\;\big[\,cos(\underbrace{kx - \omega t}_{\text{  posons }\\ kx - \omega t \,=\, \alpha} + \varphi_1) + cos(\underbrace{kx - \omega t}_{=\; \alpha} + \varphi_1)\,\big]
 &\\