Add more operators

Mathematik-V-ZF.tex

@@ -170,7 +170,9 @@ An der stelle $a$ einer Funtkion $f(x)$
 $$f(a) + \frac{f'(a)}{1!}(x-a) + \frac{f''(a)}{2!}(x-a)^2 + \frac{f'''(a)}{3!}(x-a)^3 + ...$$
 
 \section{Operators}
-$$\mathrm{rot} \ u = \nabla \times \vec{u}$$
+$$\mathrm{div} \, \vec{u} = \frac{\partial u}{\partial x} + \frac{\partial v}{\partial y}$$
+
+$$\mathrm{rot} \, \vec{u} = \nabla \times \vec{u} = -\frac{\partial u}{\partial y} + \frac{\partial v}{\partial x}$$
 
 $$\nabla = \begin{pmatrix}
     \frac{\partial}{\partial x},