Modification of the English reference course for the spherical refracting surface.

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

@@ -36,7 +36,7 @@ with :
 
 #### Spherical refracting surface.
 
-#### Analytical study of the position and shape of an image.
+#### Analytical study
 
 A **spherical refracting surface** in analytical paraxial optics is defined by *three quantities* :
 * **$`n_{ini}`$** : *refractive index of the initial medium* (the medium on the side on the incident light).
@@ -73,4 +73,4 @@ I know $`\overline{SA_{obj}}$, $n_{ini}$ and $n_{fin}$, I have previously calcul
 ! This generalizes and completes the knowledge you get about plane refracting surfaces seen in your pedagogical paths in plain and hills.
 
 
-#### Graphical study of the position and shape of an image.
+#### Graphical study