Equation 3.1.4DEF1A85BF9E8

\begin{equation} \int _{r<|y-c|<R}\operatorname {div}F\, \mathrm dy=\int _{\partial B(c,R)}F\cdot \nu \, \mathrm dS-\int _{\partial B(c,r)}F\cdot \nu \, \mathrm dS, \end{equation}