Update cheatsheet.fr.md

12.temporary_ins/20.magnetostatics-vacuum/40.ampere-theorem-applications/25.torus-solenoid/10.ampere-integral/20.overview/cheatsheet.fr.md

@@ -213,7 +213,7 @@ _puis calcul de la circulation du champ magnétique._
  $`\quad\quad\color{blue}{\scriptsize{\quad\text{En se rappelant que :}}}`$
  $`\quad\quad\color{blue}{\scriptsize{\quad\text{invariances + symétries }\Longrightarrow \vec{B}=B_{\varphi}(\rho\,,z)\,\vec{e_{\varphi}}}}`$   
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-$`\quad\quad=\oint_{\varphi=0}^{\varphi=2\pi}\big(B_{\varphi}(\rho\,,z)\,\overrightarrow{e_{\varphi}}\big)\cdot \big(+\rho\,d\varphi\,\overrightarrow{e_{\varphi}}\big)`$    
+$`\displaystyle\quad\quad=\oint_{\varphi=0}^{\varphi=2\pi}\big(B_{\varphi}(\rho\,,z)\,\overrightarrow{e_{\varphi}}\big)\cdot \big(+\rho\,d\varphi\,\overrightarrow{e_{\varphi}}\big)`$    
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 $`\displaystyle\quad\quad=\oint_{\varphi=0}^{\varphi=2\pi}B_{\varphi}(\rho\,,z)\,\rho\,\big(\overrightarrow{e_{\varphi}}\cdot \overrightarrow{e_{\varphi}}\big) d\varphi`$      
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