Update textbook.en.md

12.temporary_ins/05.coordinates-systems/30.cylindrical-coordinates/10.main/textbook.en.md

@@ -15,11 +15,10 @@ $`\def\Ssclosed{\mathscr{S}_{\scriptsize\bigcirc}}`$
 $`\def\PSopen{\mathscr{S}_{\smile}}`$
 $`\def\PSclosed{\mathscr{S}_{\displaystyle\tiny\bigcirc}}`$
 
-!!!! *LESSON IN CONSTRUCTION :* <br>
-!!!! *Not published, not visible, not yet approved*<br>
-!!!! work document only for the pedagogical team.
+!!!! *LESSON  UNDER  CONSTRUCTION :* <br>
+!!!! Published but invisible: does not appear in the tree structure of the m3p2.com site. This course is *under construction*, it is *not approved by the pedagogical team* at this stage. <br>
+!!!! Working document intended only for the pedagogical team.
 
-
-<!--MétaDonnée : INSAT-1°année_-->
+<!--MétaDonnée : INS-1°année_-->
 
 Main Part to be done