Update cheatsheet.fr.md

12.temporary_ins/40.classical-mechanics/20.n2/10.framework-of-classical-mechanics-2/20.overview/cheatsheet.fr.md

@@ -256,7 +256,7 @@ et test équivalent en html, pas en image
 </span><span style="font-family:'Times New Roman';font-weight:bold;font-size:0.9rem;color:#6699ff"> entre ces deux points.</span></p>
 
 <p style="font-family:'Times New Roman';font-weight:bold;font-size:1.3rem;text-align:left;color:#009933">Tous les observateurs partagent</p>
-<hr{width:100%;border-width:5px;border-style:solid;border-color:#009933}>
+<hr width=100% border-style="solid" color=#009933>
 <p style="font-family:'Times New Roman';font-weight:bold;font-size:1.3rem;text-align:left;color:#cccccc">un <span style="color:#0033cc"> invariant spatial</p>
 <p style="font-family:'Times New Roman';margin-left:30px;font-weight:bold;font-size:0.9rem;text-align:right;color:#6699ff">entre deux points A et B</p>
 <p style="font-family:'Times New Roman';margin-left:70px;font-size:0.9rem;font-weight:bold;text-align:right;color:#6699ff">de l'espace 3D euclidien classique</p>