diff --git a/00.brainstorming-pedagogical-teams/40.collection-existing-pedagogical-content/05.classical-mechanics/vector-analysis/textbook.fr.md b/00.brainstorming-pedagogical-teams/40.collection-existing-pedagogical-content/05.classical-mechanics/vector-analysis/textbook.fr.md
index ab91291f7..42034c9db 100644
--- a/00.brainstorming-pedagogical-teams/40.collection-existing-pedagogical-content/05.classical-mechanics/vector-analysis/textbook.fr.md
+++ b/00.brainstorming-pedagogical-teams/40.collection-existing-pedagogical-content/05.classical-mechanics/vector-analysis/textbook.fr.md
@@ -665,10 +665,18 @@ $`2\,t\,dt\cdot\overrightarrow{e_x}
 
 Por INSA / pour l'INSA / for INSA :
 
+$`\displaystyle\dfrac{d\left(\overrightarrow{OM}\right)(t)}{dt}
+=\lim_{dt\rightarrow 0}
+\left(
+\dfrac{\overrightarrow{OM}(t+dt)-\overrightarrow{OM}(t))}{dt}
+\right)`$
+
+
 $`\displaystyle\dfrac{d\left(\overrightarrow{OM}\right)(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}
 \right)`$