la divergence:
\( div\,\vec V = \frac{{\partial {V_x}}}{{\partial x}} + \frac{{\partial {V_y}}}{{\partial y}} + \frac{{\partial {V_z}}}{{\partial z}} \)
Exercice d'application:
Si \( \vec V = \left( {\matrix{ {3xy} \cr {3xz} \cr {y^2}z }} \right) \)
alors \( div\,\vec V = 3y + 0 + y^2 \)
