Update cheatsheet.en.md

01.curriculum/01.physics-chemistry-biology/02.Niv2/04.optics/04.use-of-basic-optical-elements/02.mirror/02.new-course-overview/cheatsheet.en.md

@@ -101,16 +101,16 @@ $`\overline{M_T}=-\dfrac{\overline{SA_{ima}}}{\overline{SA_{obj}}}`$  
 You know $`\overline{SA_{obj}}`$ , calculate $`\overline{SA_{ima}}`$ using (equ. 1) 
 then $`\overline{M_T}`$ with (equ.2), and deduce $`\overline{A_{ima}B_{ima}}`$.
 
-! *USEFUL 1° :<br>
+! *USEFUL 1* :<br>
 ! The conjunction equation and the transverse magnification equation for a plane mirror 
 ! are obtained by rewriting these two equations for a spherical mirror in the limit when
 ! $`|\overline{SC}|\longrightarrow\infty`$.
 ! Then we get for a plane mirror : $`\overline{SA_{ima}}=\overline{SA_{obj}}`$ and
 ! $`\overline{M_T}=+1`$.
 
-! *USEFUL 2° :<br>
-! *You can find* the conjunction and the transverse magnification **equations for a plane mirror directly from 
-! those of the spherical mirror**, with the following assumptions :<br>
+! *USEFUL 2* :<br>
+! *You can find* the conjunction and the transverse magnification *equations for a plane mirror directly from 
+! those of the spherical mirror*, with the following assumptions :<br>
 ! $`n_{eme}=-n_{inc}`$<br>
 ! (to memorize : medium of incidence=medium of emergence, therefor same speed of light, but direction
 ! of propagation reverses after reflection on the mirror)<br>