Update cheatsheet.fr.md

12.temporary_ins/10.electrostatics-vacuum/20.causes-stationary-electric-field/20.overview/cheatsheet.fr.md

@@ -777,16 +777,18 @@ figure à faire
    $`\color{blue}{\scriptsize{\text{étant } n\cdot u^{n-1}\cdot u'\;\text{, alors}}}`$   
    $`\color{blue}{\scriptsize{\text{la primitive de }  n\cdot u^{n-1}\cdot u' \text{ est } u^n}}`$   
    $`\color{blue}{\scriptsize{\text{soit encore }}}`$   
-   $`\color{blue}{\scriptsize{\text{la primitive de } u'\cdot u^n \text{ est } \dfrac{1}{n+1}\,u^{n+1}}}`$   
+   $`\color{blue}{\scriptsize{\text{la primitive de } (n+1)\cdot u^n \cdot u' \text{ est } u^{n+1}}`$   
 
    *$`\mathbf{\boldsymbol{E_M}}`$*
     $`\displaystyle\;=\dfrac{\dens^{2D}\,z_M}{2\,\epsilon_0}
     \times
     \int_{\rho=0}^{R} \rho\,(\rho^2+z_M^2)^{\,-3/2}\,d\rho`$    
     <br>
-    $`\displaystyle \hspace{1cm} =  \dfrac{\dens^{2D}\,z}{2\epsilon_0} \int_{\rho = 0}^R\dfrac{1}{2}\times
+    $`\displaystyle \hspace{1cm} =  \dfrac{\dens^{2D}\,z}{2\epsilon_0} \int_{\rho = 0}^R-\Big\underbrace{(-\dfrac{1}{2}\Big)}_{n+1}\times
     \underbrace{2\rho}_{u^{\,'}}\,\underbrace{(\rho^2+z^2)^{-\,3/2}}_{u^n}\,d\rho`$   
     <br>
+    $`\color{blue}{\scriptsize{\text{le signe moins devant } (n+1)\cdot u^n \cdot u' \text{ devient un plus en inversant les bornes d'intégration}`$ 
+    <br>
     $`\displaystyle \hspace{1cm} =  \dfrac{\dens^{2D}\,z}{2\epsilon_0} \big[\underbrace{\dfrac{1}{2}\times\dfrac{1}{-3/2+1}}
     _{=\frac{1}{2}\,\times \,(-2) \,=\, -1}(\rho^2+z^2)^{-\,1/2}\big]_0^R`$   
     <br>