Dear all,

I get stuck when I try to determine $\displaystyle U_x_x$ where $\displaystyle u(x(\xi,\eta))$

I calculate $\displaystyle u_x=\frac{\partial u}{\partial \xi}\frac{\partial \xi}{\partial x}+\frac{\partial u}{\partial \eta}\frac{\partial \eta}{\partial x}$

$\displaystyle u_x_x=\frac{\partial^{2} u}{\partial \xi^{2}}\frac{\partial^{2} \xi}{\partial x^{2}}$...... Something is telling me this is wrong but I dont know how to proceed any further

Any suggestions will be appreciated.

Thanks