Update...

Update 10.temporary-m3p2/16.waves/20.n2/10.concept-of-wave-and-wave-phenomena-2/20.overview/cheatsheet.fr.md

10.temporary-m3p2/16.waves/20.n2/10.concept-of-wave-and-wave-phenomena-2/20.overview/cheatsheet.fr.md

@@ -73,6 +73,8 @@ $`\def\PSclosed{\mathscr{S}_{\displaystyle\tiny\bigcirc}}`$
 
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+### ONDES
+
 ### **Le concept d'onde**<br>*et les phénomènes ondulatoires*   
 
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