so, i've been having trouble with this particular problem regarding proofs and partial derivatives. i get how to evaluate them but i just can't understand this problem.

ok,so for this problem, u = f(x,y), where x = e^s cost and y = e^s sin t.

show that

(∂u/∂x)^2+(∂u/∂y)^2 = e^-2s[(∂u/∂s)^2+(∂u/∂t)^2]

please help