Update textbook.fr.md

12.temporary_ins/40.classical-mechanics/30.n3/07.coherence/textbook.fr.md

@@ -572,11 +572,12 @@ $`\begin{align}
 ---------------
 
 $`\begin{align}
-\dfrac{d^2\overrightarrow{e_{\theta}}}{dt^2}&=\dfrac{d}{dt}\bigg(\underbrace{\dfrac{d\overrightarrow{e_{\theta}}}{dt}}_{=-\omega\,\vec{e_{\rho}}}\bigg)\\
+\dfrac{d^2\overrightarrow{e_{\theta}}}{dt^2}
+&=\dfrac{d}{dt}\bigg(\underbrace{\dfrac{d\overrightarrow{e_{\theta}}}{dt}}_{=-\omega\,\vec{e_{\rho}}}\bigg)\\
 \\
 &=\dfrac{d}{dt}\left(-\omega\,\overrightarrow{e_{\rho}}\right)\\
 \\
-&=-\dfrac{d\omega}{dt}\;\overrightarrow{e_{\rho}}\;-\;\omega\;\dfrac{d\overrightarrow{e_{\rho}}{dt}\\
+&=-\dfrac{d\omega}{dt}\;\overrightarrow{e_{\rho}}\;-\;\omega\;\dfrac{d\overrightarrow{e_{\rho}}}{dt}\\
 \\
 &=-\dfrac{d\omega}{dt}\;\overrightarrow{e_{\rho}}\;-\;\omega\;\big(\omega\;\overrightarrow{e_{\theta}}\big)\\
 \\