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