If $z=f(x,y)$ where $x=e^{u}cosv,y=e^{u}sinv,$ show that $y\frac{\text{d}\text{e}\text{l}\text{z}}{\text{d}\text{e}\text{l}\text{u}}+x\frac{\text{d}\text{e}\text{l}\text{z}}{\text{d}\text{e}\text{l}\text{v}}=e^{2u}\frac{\text{d}\text{e}\text{l}\text{z}}{\text{d}\text{e}\text{l}\text{y}}$