Update textbook.fr.md

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

@@ -517,7 +517,7 @@ $`\displaystyle\quad\forall \overrightarrow{V}\in\mathcal{P}\quad \overrightarro
 For the expression of a vector $`\vec{U}`$ in the base $`(\vec{e_1},\vec{e_2},...,\vec{e_n})`$,
 we should use :
 
-$`\overrightarrow{U}=\left(\begin[array](l)U_1//U_2//U_3)\end[array]\right)`$
+$`\overrightarrow{U}=\left(\begin{array}{l}U_1//U_2//U_3)\end{array}\right)`$