TeX Quellcode:

\begin{array}{rcl}f'_{xy}(x,y) &=& \dfrac{5}{9}\cos(x)e^{\sin(x)+\sin(y)}\cdot\cos(y) \\\\&=& \dfrac{5}{9}\cos(x)\cos(y)e^{\sin(x)+\sin(y)}\end{array}