# Do not get Logarithmic antiderivatives

1. May 28, 2013

### muzialis

Dear All,

the antiderivative of $$\frac{1}{x}$$ is $$ln \vert x \vert$$.
If I then consider the expression $$(x-a) ln (\vert x-a\vert)-x$$ and compute the first derivative I obtain $$ln (\vert x-a \vert)$$.
If I then consider the equivalent expression $$(x-a) ln (\vert a -x\vert)-x$$ I do not get the same result, where is my mistake??

2. May 28, 2013