Update textbook.fr.md

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

@@ -527,7 +527,10 @@ $`\quad\begin{pmatrix}U_2 V_3 - U3 V2\\U_3 V_1 - U_1 V_3\\U_1 V_2 - U_2 V_1\end{
 
 method similar to the sum used to obtain the determinant of a matrix :
 
-$`\vec{U}\land\vec{V}=\begin{vmatrix}\vec{e_1} vec{e_2} vec{e_3}\\U_1 U_2 U_3\\V_1 V_2 V_3\end{vmatrix}`$
+$`\vec{U}\land\vec{V}=\begin{vmatrix}\overrightarrow{e_1} & overrightarrow{e_2} & overrightarrow{e_3}\\
+U_1 & U_2 & U_3\\V_1 & V_2 & V_3\end{vmatrix}`$
+
+