Update textbook.fr.md

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

@@ -418,7 +418,11 @@ $`\displaystyle\quad\overrightarrow{U}\cdot\overrightarrow{V}=U_1\,V_1 + U_2\,V_
 
 $`\begin{array}{l}\left.\overrightarrow{U}\cdot\overrightarrow{V}=||\overrightarrow{U}||\cdot||\overrightarrow{V}||\cdot 
 cos (\widehat{\overrightarrow{U},\overrightarrow{V}})//
-\overrightarrow{U}\cdot\overrightarrow{V}=U_1\,V_1 + U_2\,V_2 + U_3\,V_3\right|end{array}\quad\Longrightarrow`$
+\overrightarrow{U}\cdot\overrightarrow{V}=U_1\,V_1 + U_2\,V_2 + U_3\,V_3\right|end{array}`$
+
+
+
+$`\quad\Longrightarrow`$
 $`\quad cos (\widehat{\overrightarrow{U},\overrightarrow{V}})=\dfrac{U_1\,V_1 + U_2\,V_2 + U_3\,V_3}{||\overrightarrow{U}||\cdot||\overrightarrow{V}||}`$
 $`\quad \widehat{\overrightarrow{U},\overrightarrow{V}}= arcos\left(\dfrac{U_1\,V_1 + U_2\,V_2 + U_3\,V_3}
 {||\overrightarrow{U}||\cdot||\overrightarrow{V}||}\right)`$