Add new file

12.temporary_ins/10.electrostatics-vacuum/30.gauss-theorem-demonstration/20.overview/cheatsheet.en.md

+<!--caligraphie de l'intégrale double curviligne-->
+$`\def\oiint{\displaystyle\mathop{{\iint}\mkern-18mu \scriptsize \bigcirc}}`$
+$`\def\Ltau{\Large{\tau}\normalsize}`$
+$`\def\Sopen{\mathscr{S}_{\smile}}`$
+$`\def\Sclosed{\mathscr{S}_{\displaystyle\tiny\bigcirc}}`$
+$`\def\Ssclosed{\mathscr{S}_{\scriptsize\bigcirc}}`$
+$`\def\PSopen{\mathscr{S}_{\smile}}`$
+$`\def\PSclosed{\mathscr{S}_{\displaystyle\tiny\bigcirc}}`$
+
+!!!! *LESSON UNDER CONSTRUCTION :* <br>
+!!!! *Not published, not visible, not yet approved*<br>
+!!!! Working document intended only for the pedagogical team.
+
+!  *Topic* :<br>
+! *Electrostatics / Demonstration of the Gauss's theorem, integral and local form.*<br>
+!  Starting point to establish the 3 parts: main, overview, beyond <br>
+!
+!  (_precedes the topic: Electrostatics: Application of Gauss's theorem, integral form and local form._)
\ No newline at end of file