Update textbook.fr.md

01.curriculum/01.physics-chemistry-biology/04.Niv4/04.electromagnetism/02.electromagnetic-waves-vacuum/02.electromagnetic-waves-vacuum-main/textbook.fr.md

@@ -318,7 +318,7 @@ $`\overrightarrow{E}=\left|
 
 * pour le champ magnétique :
 
-$`\hspace{1cm}\overrightarrow{B}=\left|
+$`\hspace{0.5cm}\overrightarrow{B}=\left|
    \begin{array}{r c l}
       B_x=E_O\cdot cos(\pm\,\overrightarrow{k}\cdot\overrightarrow{r}\pm \omega\,t+\phi_x))\\
       B_y=E_O\cdot cos(\pm\,\overrightarrow{k}\cdot\overrightarrow{r}\pm \omega\,t+\phi_y))\\