The first order partial derivatives are:
\begin{align*}
\frac{\partial f}{\partial x} &= -\sin x \cos y, \\
\frac{\partial f}{\partial y} &= -\cos x \sin y.
\end{align*}
The second order partial derivatives are:
\begin{align*}
\frac{\partial^2 f}{\partial x^2} &=
Show more…