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

@@ -49,6 +49,7 @@ $`\overrightarrow{rot} \, \left( \overrightarrow{rot}\,\overrightarrow{E} \right
 <br><br>
 $`\overrightarrow{rot} \, \left( \overrightarrow{rot}\,\overrightarrow{E} \right)
 =-\mu_0\;\dfrac{\partial \overrightarrow{j}}{\partial t}  +
-\mu_0 \epsilon_0 \;\dfrac{\partial^2 \overrightarrow{E}}{\partial t^2}`$<br>
+\mu_0 \epsilon_0 \;\dfrac{\partial^2 \overrightarrow{E}}{\partial t^2}`$
+<br><br>
 
 * $`\overrightarrow{grad} \left( div \; \overrightarrow{E} \right) = \overrightarrow{grad} \left( \dfrac{\rho}{\epsilon_O} \right)`$