Update textbook.en.md

10.brainstorming-innovative-courses/intercambio-curso-electromagnetismo/textbook.en.md

@@ -764,11 +764,16 @@ for all vectorial field $`\vec{X}`$,
 
 $`\displaystyle\iiint_{\tau} div\;\overrightarrow{X} \cdot d\tau = \displaystyle \oiint_{S\leftrightarrow\tau} \overrightarrow{X}\cdot\overrightarrow{dS}`$
 
+Stokes' theorem = 
 
+for all vectorial field $`\vec{X}`$, 
 
+$`\displaystyle\iint_{S\,orient.} \;\overrightarrow{rot}\;\overrightarrow{X} \cdot dS = \displaystyle \oint_{\Gamma\,orient.\overrightarrow{S}} \overrightarrow{X}\cdot\overrightarrow{dl}`$
 
 
 
+$`\displaystyle\oint_{\Gamma\,orient.}\overrightarrow{H} \cdot \overrightarrow{dl}=
+\underset{S\,orient.}{\iint{\overrightarrow{j}\cdot\overrightarrow{dS}}}`$