Update cheatsheet.fr.md

12.temporary_ins/08.conservative-vector-fields/20.conservative-vector-fields-properties/20.overview/cheatsheet.fr.md

@@ -518,7 +518,7 @@ $`\begin{align}
 & \color{blue}{\large{\mathbf{\;=-\;\overset{B}{\underset{A}{\Large{\Delta}}}(\mathcal{E}_X^{pot})}}}\\
 \end{align}`$
 <br>
-$`=-\displaystyle\,\int_A^B \alpha\,\underset{\big(\overrightarrow{grad}\,\phi_X\cdot\overrightarrow{dl}\big)}{=d\phi}`$
+$`=-\displaystyle\,\int_A^B \alpha\,\big(\underbrace{\overrightarrow{grad}\,\phi_X\cdot\overrightarrow{dl}}_{=d\phi}\big)`$
 <br>
 $`=-\displaystyle\,\int_A^B \alpha\,\underset{\underset{\big(\overrightarrow{grad}\,\phi_X\cdot\overrightarrow{dl}\big)}{=d\phi}}{par définition de $`\overrightarrow{grad}\,\phi}`$
 <br>