Update cheatsheet.fr.md

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

@@ -64,12 +64,12 @@ $`\begin{align} U(&x,t) = U_1(x,t) + U_2(x,t) \\
 &\\
 &=A\;\big[\,cos(\underbrace{kx - \omega t}_{\text{  posons }\\ kx - \omega t \,=\, \alpha} + \varphi_1) + cos(\underbrace{kx - \omega t}_{=\; \alpha} + \varphi_1)\,\big]
 &\\
-&=A\;\big[\,cos\Big(\alpha + \dfrac{\varphi_1+\varphi_1}{2} + \dfrac{\varphi_2-\varphi_2}{2}\Big) \\
-&\quad\quad + \,cos\Big(\alpha + \dfrac{\varphi_2+\varphi_2}{2} + \dfrac{\varphi_1-\varphi_1}{2}\Big)\,\Big]\\
+&=A\;\big[\,cos\Big(alpha + \dfrac{\varphi_1+\varphi_1}{2} + \dfrac{\varphi_2-\varphi_2}{2}\Big) \\
+&\quad\quad\quad + \,cos\Big(\alpha + \dfrac{\varphi_2+\varphi_2}{2} + \dfrac{\varphi_1-\varphi_1}{2}\Big)\,\Big]\\
+&\\
+&=A\;\big[\,cos\Big(\underbrace{alpha + \dfrac{\varphi_1+\varphi_2}{2}}_{\alpha '} + \dfrac{\varphi_1-\varphi_2}{2}\Big) \\
+&\quad\quad\quad + \,cos\Big(\underbrace{\alpha + \dfrac{\varphi_1+\varphi_2}{2}}_{\text{nous avons posé}\\\alpha + \dfrac{\varphi_1+\varphi_2}{2} = \alpha '} - \dfrac{\varphi_1-\varphi_1}{2}\Big)\,\Big]\\
 &\\
-&=A\;\big[\,cos\Big(\alpha + \dfrac{\varphi_1+\varphi_2)}{2} + \dfrac{\varphi_1-\varphi_2)}{2}\Big) + \,cos\Big(\alpha + \dfrac{\varphi_1+\varphi_2)}{2} - \dfrac{\varphi_1-\varphi_2)}{2}\Big)\,\Big]
-     \end{align}`$
-
 
 * L'onde résultante $`U = U_1 + U_2`$ :   
   $`\begin{align} U(x,t) &= U_1(x,t) + U_2(x,t) \\