show d2z/dx2+d2z/dy2 = e-2s[d2z/ds2+ d2/dt2
The product rule
The Attempt at a Solution
I found d2x/dt2=2e2ssin(t)cos(t)d2z/dydx + e2scos2(t)dz/dy2
But, now I'm lost. It doesn't seem to be going anywhere. I don't know where I am going to get rid of the d2z/dydx term.
Thank your for your help.