Update textbook.fr.md

00.brainstorming-pedagogical-teams/40.collection-existing-pedagogical-content/05.classical-mechanics/vector-analysis/textbook.fr.md

@@ -679,6 +679,13 @@ $`\displaystyle\dfrac{d\left(\overrightarrow{OM}\right)(t)}{dt}
 \right)`$
 $`=\dfrac{\overrightarrow{OM}(t+dt)-\overrightarrow{OM}(t)}{dt}`$
 
+$`\displaystyle\dfrac{d\overrightarrow{OM}(t)}{dt}
+=\lim_{\Delta t\rightarrow 0}
+\left(
+\dfrac{\overrightarrow{OM}(t+\Delta t)-\overrightarrow{OM}(t))}{\Delta t}
+\right)`$
+$`=\dfrac{\overrightarrow{OM}(t+dt)-\overrightarrow{OM}(t)}{dt}`$
+