Update textbook.fr.md

00.brainstorming-pedagogical-teams/40.collection-existing-pedagogical-content/04.reference-frames-coordinate-systems/textbook.fr.md

@@ -225,7 +225,7 @@ In Cartesian coordinates, the base vectors keep the
 **same direction whatever the position of the point $`M`$**.<br>
 <br>$`(\overrightarrow{e_x},\overrightarrow{e_y},\overrightarrow{e_z})`$ 
 base ortogonal independiente de la posición de $`M`$ / base orthogonale indépendante
-de la position de $`M`$ / orthogonal basis independent of the position of $`M`$.
+de la position de $`M`$ / orthogonal basis independent of the position of $`M`$.<br>
 <br>$`||\overrightarrow{e_x}||=||\overrightarrow{e_y}||=||\overrightarrow{e_z}||=1`$<br>
 $`\overrightarrow{e_x}\perp\overrightarrow{e_y}\quad,\quad\overrightarrow{e_y}
 \perp\overrightarrow{e_z}\quad,\quad\overrightarrow{e_x}\perp\overrightarrow{e_z}`$<br>