Thanks. Given that, here's the sagenb (4.7.2) version, showing the bug
(wrong when t is negative real):
sage: t=var('t')
sage: f=(1/2)*log(2*t)+(1/2)*log(1/t)
sage: f.full_simplify()
1/2*log(2)
[William - this is actually quite a difficult area: see Beaumont et
al.,
Testing Elementary Function Identities Using CAD.
AAECC 18(2007) pp. 513-543.
http://www.springerlink.com/content/f1357425727485r0.]
On Jan 14, 7:22 pm, William Stein <wst...@gmail.com> wrote:
> On Sat, Jan 14, 2012 at 10:00 AM, JamesHDavenport
>
> <j.h.davenp...@bath.ac.uk> wrote:
> > I was using sagenb,org, so the output isn't actually a SAGE session,
> > but pasting from sagenb.org. It says it is 4.7.2.
> > Glad it's fixed. I guess I ought to download a 4.8 if I'm really going
> > to comment in more detail, given the apparent changes.
>
> Quick hint: If you click the Text button in the upper right of the
> notebook, you'll get something that looks like a normal Sage session.
>
>
>
>
>
>
>
>
>
>
>
> > On Jan 14, 1:47 am, Michael Orlitzky <mich...@orlitzky.com> wrote:
> >> On 01/13/2012 07:38 PM, JamesHDavenport wrote:
>
> >> > Unfortunately, full_simplify has its own problems, notably with branch
> >> > cuts.
> >> > sage: f = (1/2)*log(2*t) + (1/2)*log(-t)
> >> > sage: f.full_simplify()
> >> > 1/2*log(2)
>
> >> In my session, I had the difference of two logarithms. In yours above,
> >> you've got the sum. Is that an actual sage session? I get something
> >> different on 4.8.alpha6:
>
> >> sage: f = (1/2)*log(2*t) + (1/2)*log(-t)
> >> sage: f.full_simplify()
> >> 1/2*I*pi + 1/2*log(2) + log(t)
>
> >> In the example below, with t=-1, both logs should have imaginary part pi
> >> and real parts log(2) and zero respectively?
>
> >> >> There's no global function for it, but what you want is to call
> >> >> full_simplify() on the expression.
>
> >> >> sage: f = (1/2)*log(2*t) - (1/2)*log(t)
> >> >> sage: f.full_simplify()
> >> >> 1/2*log(2)
>
> > --
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>
> --
> William Stein
> Professor of Mathematics
> University of Washingtonhttp://wstein.org
>
> Screen Shot 2012-01-14 at 11.21.58 AM.png
> 73KViewDownload
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