Update cheatsheet.fr.md

12.temporary_ins/20.magnetostatics-vacuum/40.ampere-theorem-applications/30.cylindrical-current-distributions/20.solenoidal-current/10.ampere-integral/20.overview/cheatsheet.fr.md

@@ -244,6 +244,13 @@ $`\Longrightarrow\quad\overrightarrow{dl} \cdot \overrightarrow{B}=0`$
     {\color{blue}{=\,0}}
     \end{align}`$
 
+* **$`\mathbf{\oint_{\Gamma_A}\overrightarrow{B}\cdot\overrightarrow{dl}}`$**
+     $`\begin{align}=&\int_D^A \overrightarrow{B}\cdot\,dz\overrightarrow{e_z} + \int_A^B \underbrace{\overrightarrow{B}\cdot\overrightarrow{dl}}_
+    {\color{blue}{=\,0}}\\
+             &\int_B^C \overrightarrow{B}\cdot\,dz\overrightarrow{e_z} + \int_C^D \underbrace{\overrightarrow{B}\cdot\overrightarrow{dl}}_
+    {\color{blue}{=\,0}}
+    \end{align}`$
+