Update textbook.fr.md

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

@@ -665,8 +665,9 @@ $`2\,t\,dt\cdot\overrightarrow{e_x}
 
 Por INSA / pour l'INSA / for INSA :
 
-$`\displaystyle\dfrac{d\left(\overrightarrow{OM}\right)(t)}{dt}=\lim_{\Delta t\rightarrow 0}
-\left(\dfrac{\overrightarrow{OM}\right)(t+\Delta t)-\overrightarrow{OM}\right)(t))}{\Delta t}`$
+$`\displaystyle\dfrac{d\left(\overrightarrow{OM}\right)(t)}{dt}
+=\lim_{\Delta t\rightarrow 0}
+\left(\dfrac{\overrightarrow{OM}\right)(t+\Delta t)-\overrightarrow{OM}\right)(t))}{\Delta t}\right)`$