TeX Quellcode:

\begin{array}{rcl}f'_{xx}(x,y) &=&-4\sin(x)\\& & +\dfrac{1}{4}\cos\left(-\dfrac{1}{4}x+y\right)\cdot \left(-\dfrac{1}{4}\right)\\&=& -4\sin(x)-\dfrac{1}{16}\cos\left(-\dfrac{1}{4}x+y\right)\end{array}