- #1

[tex]v(x,y)=u(r(x,y),s(x,y))[/tex]

(derivations)

At some point I come across this:

[tex]\frac{\partial}{\partial x} \frac{\partial u}{\partial r}[/tex]

which I wrote as

[tex]\frac{\partial^2 u}{\partial r^2} \frac{\partial r}{\partial x}[/tex]

Is it right?