allgemein E = y' * x / y hier also
E = x ' (h) * h / x (h)
und x (h) = √(a/h) = h^{-1/2} * √a ==> x ' (h) = -(1/2) * h^{-3/2} * √a
Also E = -(1/2) * h^{-3/2} * √a * h / ( h^{-1/2} * √a )
= -(1/2) * h^{-1/2} * √a / ( h^{-1/2} * √a ) dann Kürzen !
= -(1/2)