Update cheatsheet.fr.md

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

@@ -1675,18 +1675,15 @@ $`= 2\,A\,\,cos\big(\Delta \omega_{1-2} t + \varphi_B) \times cos\,(\omega_{moy}
   **$`\mathbf{U(t)=U(t+T)}`$**   
   <br>
   $`\begin{align}
-  \quad\Longleftrightarrow &cos^2\left(2\pi\dfrac{\nu_1 - \nu_2}{2} t + \varphi_B\right)\\
-  &\quad\quad\quad = cos^2\left(2\pi\dfrac{\nu_1 - \nu_2}{2} (t + \mathbf{\color{blue}{T}}) + \varphi_B\right)
-  \end{align)`$   
-  <br>
-  $`\begin{align}\quad\Longleftrightarrow &cos^2\left(2\pi\dfrac{\nu_1 - \nu_2}{2} t + \varphi_B\right)\\
-  &\quad\quad\quad = cos^2\left(2\pi\dfrac{\nu_1 - \nu_2}{2} (t + \mathbf{\color{blue}{T}}) + \varphi_B\right)\end{align)`$   
+  \quad\Longleftrightarrow &cos^2\left(2\pi\dfrac{\nu_1 - \nu_2}{2} t + \varphi_B\right) \\
+  &\quad\quad\quad = cos^2\left(2\pi\dfrac{\nu_1 - \nu_2}{2} (t + \color{blue}{\mathbf{T}}) + \varphi_B\right)
+  \end{align}`$   
   <br>
   $`\begin{align}\quad\Longleftrightarrow & cos^2\big(\pi (\nu_1 - \nu_2) t + \varphi_B\big)\\
   &\quad\quad\quad =cos^2\big(\underbrace{\pi (\nu_1 - \nu_2) t + \varphi_B \pm \mathbf{\color{blue}{\pi}}}_{
-  \color{blue}{+\;\Longleftrightarrow \nu_1 - \nu_2\gt 0 \\ -\;\Longleftrightarrow \nu_1 - \nu_2\gt 0}}\big)\end{align)`$ 
+  \color{blue}{+\;\Longleftrightarrow \nu_1 - \nu_2\gt 0 \\ -\;\Longleftrightarrow \nu_1 - \nu_2\gt 0}}\big)\end{align}`$ 
   <br>
-  $`\quad\Longleftrightarrow 2pi |\,\nu_1 - \nu_2\,| T = \pi`$   
+  $`\quad\Longleftrightarrow \pi\, |\,\nu_1 - \nu_2\,|\, T = \pi`$   
   <br>
   **$`\quad\Longleftrightarrow \mathbf{T = |\,\nu_1 - \nu_2\,|}`$**