If $\displaystyle u=f(x,y)$, where $\displaystyle x=e^scos(t)$ and $\displaystyle y=e^ssin(t)$, show that
$\displaystyle \partial^2u/(\partial*x^2)+\partial^2u/(\partial*y^2)=e^-^2^s[\partial^2u/(\partial*s^2)+\partial^2u/(\partial*t^2)]$
If $\displaystyle u=f(x,y)$, where $\displaystyle x=e^scos(t)$ and $\displaystyle y=e^ssin(t)$, show that
$\displaystyle \partial^2u/(\partial*x^2)+\partial^2u/(\partial*y^2)=e^-^2^s[\partial^2u/(\partial*s^2)+\partial^2u/(\partial*t^2)]$