Update cheatsheet.fr.md

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

@@ -67,8 +67,11 @@ $`\begin{align} U(&x,t) = U_1(x,t) + U_2(x,t) \\
 &=A\;\big[\,cos\Big(\alpha + \dfrac{\varphi_1+\varphi_1}{2} + \dfrac{\varphi_2-\varphi_2}{2}\Big) \\
 &\quad\quad\quad + \,cos\Big(\alpha + \dfrac{\varphi_2+\varphi_2}{2} + \dfrac{\varphi_1-\varphi_1}{2}\Big)\,\Big]\\
 &\\
-&=A\;\big[\,cos\Big(\underbrace{\alpha + \dfrac{\varphi_1+\varphi_2}{2}}_{\alpha '} + \dfrac{\varphi_1-\varphi_2}{2}\Big) \\
-&\quad\quad\quad + \,cos\Big(\underbrace{\alpha + \dfrac{\varphi_1+\varphi_2}{2}}_{\text{nous avons posé }\\ \alpha + (\varphi_1+\varphi_2)/2 = \alpha '} - \dfrac{\varphi_1-\varphi_1}{2}\Big)\,\Big]\\
+&=A\;\big[\,cos\Big(\underbrace{\alpha + \dfrac{\varphi_1+\varphi_2}{2}}_{=\;\alpha '} + \dfrac{\varphi_1-\varphi_2}{2}\Big) \\
+&\quad\quad\quad + \,cos\Big(\underbrace{\alpha + \dfrac{\varphi_1+\varphi_2}{2}}_{\text{nous avons posé }\\ \alpha + (\varphi_1+\varphi_2)/2\; = \;\alpha '} - \dfrac{\varphi_1-\varphi_2}{2}\Big)\,\Big]\\
+&\\
+&=A\;\big[\,cos\Big(\alpha ' + \dfrac{\varphi_1-\varphi_2}{2}\Big) \\
+&\quad\quad\quad + \,cos\Big(\alpha ' - \dfrac{\varphi_1-\varphi_2}{2}\Big)\,\Big]\\
 &\\
   \end{align}`$
 * L'onde résultante $`U = U_1 + U_2`$ :