Update cheatsheet.fr.md

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

@@ -60,11 +60,17 @@ $`\newcommand{\ddpt}[1]{\overset{\large\bullet\bullet}{#1}}`$
   &=\sqrt{4\,A^2 \cdot cos\Big(\dfrac{\varphi_1 - \varphi_2}{2}\Big)\,cos\Big(\dfrac{\varphi_1 - \varphi_2}{2}\Big)}
   \end{align}`$
 
-\underbrace{  {toto}
-
-      {\left.\begin{align} cos(a+b)=cos(a)cos(b)-sin(a)sin(b)\\
+  $`\begin{align} A_{onde} &= \left| \,2\,A\cdot cos\Big(\dfrac{\varphi_1 - \varphi_2}{2} \Big) \,\right|\\
+  &\\
+  &=\sqrt{4\,A^2 \cdot \underbrace{cos\Big(\dfrac{\varphi_1 - \varphi_2}{2}\Big)\,cos\Big(\dfrac{\varphi_1 - \varphi_2}{2}\Big)}
+  _{\left.\begin{align} cos(a+b)=cos(a)cos(b)-sin(a)sin(b)\\
                      cos(a-b)=cos(a)cos(b)+-sin(a)sin(b)\end{align}\right\}\Rightarrow\\
         cos(a)cos(a)=cos^2(a)=\frac{1}{2}[cos(a+a)+cos(a-a)]frac{1}{2}[1 + cos(2a)]}
+  }\end{align}`$
+
+\underbrace{  {toto}
+
+      {
 
 
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