diff --git a/01.curriculum/01.physics-chemistry-biology/02.Niv2/04.optics/04.use-of-basic-optical-elements/01.plane-refracting-surface/02.plane-refracting-surface-overview/cheatsheet.en.md b/01.curriculum/01.physics-chemistry-biology/02.Niv2/04.optics/04.use-of-basic-optical-elements/01.plane-refracting-surface/02.plane-refracting-surface-overview/cheatsheet.en.md
index c622b725b..a52c22782 100644
--- a/01.curriculum/01.physics-chemistry-biology/02.Niv2/04.optics/04.use-of-basic-optical-elements/01.plane-refracting-surface/02.plane-refracting-surface-overview/cheatsheet.en.md
+++ b/01.curriculum/01.physics-chemistry-biology/02.Niv2/04.optics/04.use-of-basic-optical-elements/01.plane-refracting-surface/02.plane-refracting-surface-overview/cheatsheet.en.md
@@ -132,7 +132,7 @@ which defines $`\overline{SC}`$ : algebraic distance between vertex S and center
 \- **$`n_{eme}`$ : refractive index of the medium of the emergent light**.
 
 * 1 arrow : indicates the *direction of light propagation*
-* 
+
 ![](dioptre-1.gif)
 
 
@@ -148,14 +148,16 @@ which defines $`\overline{SC}`$ : algebraic distance between vertex S and center
 You know $`\overline{SA_{obj}}`$, $`n_{inc}`$ and $`n_{eme}`$, you have previously calculated $`\overline{SA_{ima}}`$, so you can calculate $`\overline{M_T}`$ and deduced $`\overline{A_{ima}B_{ima}}`$.
 
 
-! *USEFUL* : The conjuction equation and the transverse magnification equation for a plane refracting surface are obtained by rewriting these equations for a spherical refracting surface in the limit when $`|\overline{SC}|\longrightarrow\infty`$.<br> Then we get *for a plane refracting surface :*
+! *USEFUL* : The conjuction equation and the transverse magnification equation for a plane refracting 
+!surface are obtained by rewriting these equations for a spherical refracting surface in the limit when
+! $`|\overline{SC}|\longrightarrow\infty`$.<br> Then we get *for a plane refracting surface :*
 !
 ! * *conjuction equation :*&nbsp;&nbsp; $`\dfrac{n_{fin}}{\overline{SA_{ima}}}-\dfrac{n_{ini}}{\overline{SA_{obj}}}=0`$ &nbsp;&nbsp; (equ.3)
 !
 ! * *transverse magnification equation :*&nbsp;&nbsp; $`\dfrac{n_{ini}\cdot\overline{SA_{ima}}}{n_{fin}\cdot\overline{SA_{obj}}}`$
 &nbsp;&nbsp; (equ.2, unchanged)<br><br>
-but (equ.3) gives $`\dfrac{\overline{SA_{ima}}}{\overline{SA_{obj}}}=\dfrac{n_{inc}}{n_{eme}}`$.<br>
-Copy this result into (equ.2) leads to $`\overline{M_T}=+1`$.
+! but (equ.3) gives $`\dfrac{\overline{SA_{ima}}}{\overline{SA_{obj}}}=\dfrac{n_{inc}}{n_{eme}}`$.<br>
+! Copy this result into (equ.2) leads to $`\overline{M_T}=+1`$.
 
 
 #### Graphical study
\ No newline at end of file