Update cheatsheet.fr.md

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

@@ -488,7 +488,7 @@ $`\boldsymbol{\mathbf{\cdot\big(-\,R\,\overrightarrow{e_{\rho}}\,+\,z_M\,\overri
    **$`\boldsymbol{\mathbf{E_M}}`$**
    *$`\displaystyle\boldsymbol{\mathbf{\;=\int_{\varphi = 0}^{2\pi}\dfrac{\dens^{1D}}{4\pi\epsilon_0}\cdot\dfrac{R\,z_M}{d^2}\,d\varphi}}`$*   
    <br>
-   $`\displaystyle\hspace{2.3cm}=\dfrac{\dens^{1D}}{4\pi\epsilon_0}\cdot\dfrac{R\,z_M}{d^2}\;\int_{\varphi = 0}^{2\pi}\,d\varphi`$   
+   $`\displaystyle\hspace{2.3cm}=\dfrac{\dens^{1D}}{4\pi\epsilon_0}\cdot\dfrac{R\,z_M}{d^2}\;\underbrace{\int_{\varphi = 0}^{2\pi}\,d\varphi}_{\color{blue}{=\big[\varphi\big]_0^{2\pi}\\=„\pi}}`$   
    <br>
    **$`\boldsymbol{\mathbf{\hspace{2.3cm}=\dfrac{\dens^{1D}}{2\epsilon_0}\cdot\dfrac{R\,z_M}{d^2}}}`$**