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

@@ -4,3 +4,6 @@ published : false
 visible : false
 ---
 $`\overrightarrow{rot}\,\overrightarrow{E}=-\dfrac{\partial \overrightarrow{B}}{\partial t}`$
+
+$`\overrightarrow{rot} \, \left( \overrightarrow{rot}\,\overrightarrow{E} \right)=
+\overrightarrow{rot} \,\left( -\dfrac{\partial \overrightarrow{B}}{\partial t}\right)`$