diff --git a/00.brainstorming-pedagogical-teams/40.collection-existing-pedagogical-content/04.reference-frames-coordinate-systems/textbook.fr.md b/00.brainstorming-pedagogical-teams/40.collection-existing-pedagogical-content/04.reference-frames-coordinate-systems/textbook.fr.md
index ea814624f..5f238322f 100644
--- a/00.brainstorming-pedagogical-teams/40.collection-existing-pedagogical-content/04.reference-frames-coordinate-systems/textbook.fr.md
+++ b/00.brainstorming-pedagogical-teams/40.collection-existing-pedagogical-content/04.reference-frames-coordinate-systems/textbook.fr.md
@@ -670,9 +670,12 @@ en coordenadas cilíndricas son :
coordonnées cylindriques sont :
[EN] According to the chosen direction, the **scalar surface elements $`dA`$** in
cylindrical coordinates are :
-
$`dA_{\rho\varphi}=dl_{\rho}\;dl\varphi=d\rho\cdot\rho\;d\varphi\quad`$,
-$`\quad dA_{\rho z}=dl_{\rho}\;dlz=d\rho\;dz\quad`$, $`\quad dA_{\varphi z}
-=dl_{\varphi}\;dlz=\rho\,d\varphi\;dz`$
+
$`dA_{\rho\varphi}=dl_{\rho}\;dl\varphi=d\rho\cdot\rho\;d\varphi\quad`$,
+en una superficie tal que $`z=cst`$.
+$`dA_{\rho z}=dl_{\rho}\;dlz=d\rho\;dz\quad`$,
+en una superficie tal que $`\varphi=cst`$.
+$`dA_{\varphi z}=dl_{\varphi}\;dlz=\rho\,d\varphi\;dz`$
+en una superficie tal que $`\rho=cst`$.