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 ae63fe679..811d33375 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
@@ -45,16 +45,13 @@ A **spherical refracting surface** in analytical paraxial optics is defined by *
 
 ! *USEFUL* : The whole analytic study below also applies to a plane refracting surface. We just need to remark that a plane surface is a spherical surface whose radius of curvature tends towards infinity.
 
-Consider a *point object* **$`B_{obj}`$** whose orthogonal projection on the optical axis gives the *point object*  **$`A_{obj}`$**. If the point object is located on the optical axis, then $`B_{obj}=A_{obj}`$ and we will use to named it point object $`A_{obj}`$. The point object $`B_{obj}`$ can be **real** *as well as* **virtual**.
+##### Spherical refracting surface equation
 
-The **calculation of the position** of the *point image* **$`B_{ima}`$**, *conjugated point of the point object $`B_{obj}`$* by the refracting surface, is carried out in **two steps** :
-
-1.  I use the **spherical refracting surface equation** (known too as the **"conjuction equation" for a spherical refracting surface**) to calculate the *position of the point* **$`A_{ima}`$**, $`A_{ima}`$ being the *orthogonal projection on the optical axis of the point image* $`B_{ima}`$. 
+**spherical refracting surface equation** = **"conjuction equation" for a spherical refracting surface**
 
 **$`\dfrac{n_{fin}}{\overline{SA_{ima}}}-\dfrac{n_{ini}}{\overline{SA_{obj}}}=\dfrac{n_{fin}-n_{ini}}{\overline{SC}}`$**
 
-To perform this I *need to know the __algebraic distance__* **$`\overline{SA_{obj}}`$**, and the *calculation  of the __algebraic distance__* **$`\overline{SA_{ima}}`$** along the optical axis *gives me the position of $`A_{ima}`$*.
-<!--conjugación-->
+##### Transverse magnification expression
 
 2. I use the **"transverse magnification equation" for a spherical refracting surface**, to calculate the *__algebraic value__ of the transverse magnification* **$`\overline{M_T}`$**, then to derive the *__algebraic length__* **$`\overline{A_{ima}B_{ima}}`$** of the segment $`[A_{ima}B_{ima}]`$, that is the algebraic distance of the point image $`B_{ima}`$ from its orthogonal projection $`A_{ima}`$ on the optical axis.