Update cheatsheet.fr.md

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

@@ -56,9 +56,9 @@ $`\newcommand{\ddpt}[1]{\overset{\large\bullet\bullet}{#1}}`$
 
 * Son amplitude est :   
   <br>
-  **$`A_{résult.} &= \left| \,2\,A\cdot cos\Big(\dfrac{\varphi_1 - \varphi_2}{2} \Big) \,\right|`$**   
+  **$`A_{résult.} = \left| \,2\,A\cdot cos\Big(\dfrac{\varphi_1 - \varphi_2}{2} \Big) \,\right|`$**   
   <br>
-  $`\quad\quad=\sqrt{4\,A^2 \cdot cos^2\Big(\dfrac{\varphi_1 - \varphi_2}{2}\Big)}`$   
+  $`\quad\quad=\sqrt{4\,A^2 \cdot cos^2\Big(\dfrac{\varphi_1 - \varphi_2}{2}\Big)`$   
   <br>
   $`\color{blue}{\scriptsize{\left.\begin{align} \quad\quad &cos(a+b)=cos(a)cos(b)-sin(a)sin(b)\\
                      &cos(a-b)=cos(a)cos(b)+-sin(a)sin(b)\end{align}