diff --git a/01.curriculum/01.physics-chemistry-biology/04.Niv4/04.electromagnetism/02.electromagnetic-waves-vacuum/02.electromagnetic-waves-vacuum-main/textbook.fr.md b/01.curriculum/01.physics-chemistry-biology/04.Niv4/04.electromagnetism/02.electromagnetic-waves-vacuum/02.electromagnetic-waves-vacuum-main/textbook.fr.md
index 71016174e..9bbded7cf 100644
--- a/01.curriculum/01.physics-chemistry-biology/04.Niv4/04.electromagnetism/02.electromagnetic-waves-vacuum/02.electromagnetic-waves-vacuum-main/textbook.fr.md
+++ b/01.curriculum/01.physics-chemistry-biology/04.Niv4/04.electromagnetism/02.electromagnetic-waves-vacuum/02.electromagnetic-waves-vacuum-main/textbook.fr.md
@@ -70,5 +70,6 @@ $`\Delta \;\overrightarrow{E} = \overrightarrow{grad}\left( \dfrac{\rho}{\epsilo
 
 ce qui donne par identification au premier terme de l'équation d'onde :
 
-$`\Delta \;\overrightarrow{E}-\mu_0 \epsilon_0 \;\dfrac{\partial^2 \overrightarrow{E}}{\partial t^2} = \overrightarrow{grad}\left( \dfrac{\rho}{\epsilon_O} \right) + \mu_0\;\dfrac{\partial \overrightarrow{j}}{\partial t}  +
+$`\Delta \;\overrightarrow{E}-\mu_0 \epsilon_0 \;\dfrac{\partial^2 \overrightarrow{E}}{\partial t^2} = \dfrac{1}{\epsilon_O} \;
+\overrightarrow{grad}\left(\rho \right) + \mu_0\;\dfrac{\partial \overrightarrow{j}}{\partial t}  +
 \mu_0 \epsilon_0 \;\dfrac{\partial^2 \overrightarrow{E}}{\partial t^2}`$