Update cheatsheet.fr.md

12.temporary_ins/40.classical-mechanics/30.n3/40.point-dynamics/20.overview/cheatsheet.fr.md

@@ -241,7 +241,8 @@ $`\hspace{0.5cm}=\dfrac{d\overrightarrow{p}}{dt}`$
 <br>
 $`\hspace{0.5cm}=\dfrac{d\big(m\overrightarrow{v}\big)}{dt}`$   
 <br>
-**$`\Large\mathbf{\hspace{0.5cm}=m\,\overrightarrow{a}\;+\underbrace{\dfrac{dm}{dt}\cdot\overrightarrow{v}}_{\color{blue}{\text{  si masse}\\\text{non constante}}}`$**
+**$`\Large\mathbf{\hspace{0.5cm}=m\,\overrightarrow{a}\;+\underbrace{\dfrac{dm}{dt}\cdot\overrightarrow{v}}_{\color{blue}
+{\text{  si masse}\\ \text{non constante}}}`$**
 
 
 <!----------------------