Wrong simplification of log(1/z)



-----maxima-bounces at math.utexas.edu wrote: -----

>Unfortunately, I have found the following wrong simplification:
>
>(%i49) 1/2*(log(z)-log(1/z))-log(z);
>(%o49) 0
>
>The reason is that Maxima simplifies:
>
>(%i50) log(1/z);
>(%o50) -log(z)
>
>But that is wrong for z an element of (-inf,0).

Maybe you want to set logexpand to false, or maybe you need to use plog
instead of log:

(%i1) log(1/z), logexpand : false;
(%o1) log(1/z)

(%i2) plog(1/z);
Is  z   positive or negative? pos;
(%o2) -log(z)

(%i3) declare(z,complex)$

(%i4) plog(1/z);
(%o4) plog(1/z)

Barton