对数导数的推导

对数导数的推导
D(In(x))
GO
{In(x+small_x)-In(x)}/small_x
Go
In(1+small_x/x)/small_x
Go
In {(1+small_x/x)}^(1/small_x)
设small_x/x=1/t,
Go
In (1+1/t)^(t/x)
Go
In e^(1/x)
GO
1/x