Update cheatsheet.en.md

01.curriculum/01.physics-chemistry-biology/02.Niv2/04.optics/04.use-of-basic-optical-elements/03.lens/02.new-course-overview/cheatsheet.en.md

@@ -66,7 +66,7 @@ with $V (\delta)=\dfrac{1}{f'(m)}$ ($f'$ being expresssed in m "meter" and $V$ i
 ![](lens-divergent-N2-en.jpeg)
 
 * Characterized by :<br>
-\- **Focal lenght** (usually in cm) always <0 *+* adjective "**diverging**"<br>
+\- **Focal lenght** (usually in cm) always >0 *+* adjective "**diverging**"<br>
 &nbsp;&nbsp;or<br>
 \- Its **image focal length** $f'$ (in *algebraic value*, usually in cm), that is *negative $f'<0$*.<br>
 &nbsp;&nbsp;or<br>